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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2015	Oct. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	ALEXANDERS INC
Entity Central Index Key	0000003499
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		5,106,196
Trading Symbol	alx

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Real estate, at cost:
Land	$ 44,971	$ 44,971
Buildings and leasehold improvements	950,416	873,667
Development and construction in progress	40,189	75,289
Total	1,035,576	993,927
Accumulated depreciation and amortization	(229,498)	(210,025)
Real estate, net	806,078	783,902
Cash and cash equivalents	252,866	227,815
Short-term investments	0	24,998
Restricted cash	84,770	84,602
Marketable securities	41,119	44,646
Tenant and other receivables, net of allowance for doubtful accounts of $1,051 and $1,544, respectively	2,772	2,213
Receivable arising from the straight-lining of rents	181,215	179,939
Deferred lease and other property costs, net, including unamortized leasing fees to Vornado of $31,796 and $33,974, respectively	43,756	46,561
Deferred debt issuance costs, net of accumulated amortization of $3,626 and $11,295, respectively	6,964	4,824
Other assets	37,161	23,716
Total assets	1,456,701	1,423,216
LIABILITIES AND EQUITY
Mortgages payable	1,060,408	1,032,780
Amounts due to Vornado	5,966	3,922
Accounts payable and accrued expenses	42,238	35,127
Other liabilities	2,965	2,988
Total liabilities	1,111,577	1,074,817
Commitments and contingencies
Preferred stock: $1.00 par value per share; authorized, 3,000,000 shares; issued and outstanding, none	0	0
Common stock: $1.00 par value per share; authorized, 10,000,000 shares; issued, 5,173,450 shares; outstanding, 5,106,196 shares	5,173	5,173
Additional capital	30,739	30,139
Retained earnings	298,664	299,004
Accumulated other comprehensive income	10,922	14,457
Equity before treasury stock	345,498	348,773
Treasury stock: 67,254 shares, at cost	(374)	(374)
Total equity	345,124	348,399
Total liabilities and equity	$ 1,456,701	$ 1,423,216

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets
Allowance for doubtful accounts (in US dollars)	$ 1,051	$ 1,544
Unamortized leasing fees to Vornado (in US dollars)	31,796	33,974
Deferred debt issuance costs, accumulated amortization (in US dollars)	$ 3,626	$ 11,295
Preferred stock: par value per share (in dollars per share)	$ 1.00	$ 1.00
Preferred stock: authorized shares	3,000,000	3,000,000
Preferred stock: issued shares	0	0
Preferred stock: outstanding shares	0	0
Common stock: par value per share (in dollars per share)	$ 1.00	$ 1.00
Common stock: authorized shares	10,000,000	10,000,000
Common stock: issued shares	5,173,450	5,173,450
Common stock: outstanding shares	5,106,196	5,106,196
Treasury stock: shares	67,254	67,254

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
REVENUES
Property rentals	$ 34,599	$ 33,984	$ 103,654	$ 102,166
Expense reimbursements	17,815	16,093	51,442	47,362
Total revenues	52,414	50,077	155,096	149,528
EXPENSES
Operating, including fees to Vornado of $1,081, $1,223, $3,298 and $3,369, respectively	19,390	17,299	55,985	50,939
Depreciation and amortization	8,092	7,271	22,783	21,812
General and administrative, including management fees to Vornado of $595 and $1,785 in each three and nine month period, respectively	1,091	1,127	4,261	3,872
Total expenses	28,573	25,697	83,029	76,623
OPERATING INCOME	23,841	24,380	72,067	72,905
Interest and other income, net	427	409	1,237	1,235
Interest and debt expense	(6,094)	(7,446)	(19,963)	(24,720)
Income before income taxes	18,174	17,343	53,341	49,420
Income tax (expense) benefit	(2)	349	(6)	344
Net income	$ 18,172	$ 17,692	$ 53,335	$ 49,764
Net income per common share- basic and diluted (in dollars per share)	$ 3.55	$ 3.46	$ 10.43	$ 9.74
Weighted average shares outstanding- basic and diluted (in shares)	5,113,077	5,111,201	5,112,108	5,110,435
Dividends per common share (in dollars per share)	$ 3.50	$ 3.25	$ 10.50	$ 9.75

Consolidated Statements of Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Consolidated Statements of Income
Fees to Vornado	$ 1,081	$ 1,223	$ 3,298	$ 3,369
Management fees to Vornado	$ 595	$ 595	$ 1,785	$ 1,785

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 18,172	$ 17,692	$ 53,335	$ 49,764
Other comprehensive income:
Change in unrealized net gain on available-for-sale securities	1,188	(1,563)	(3,527)	2,644
Change in value of interest rate cap	2	(30)	(8)	(183)
Comprehensive Income	$ 19,362	$ 16,099	$ 49,800	$ 52,225

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock
Shares Issued, Beginning Balance (in shares) at Dec. 31, 2013		5,173,000
Balance, at Dec. 31, 2013	$ 333,581	$ 5,173	$ 29,745	$ 297,515	$ 1,522	$ (374)
Net income	49,764			49,764
Dividends paid	(49,825)			(49,825)
Change in unrealized net gain on available-for-sale securities	2,644				2,644
Change in value of interest rate cap	(183)				(183)
Deferred stock unit grants	394		394
Shares Issued, Ending Balance (in shares) at Sep. 30, 2014		5,173,000
Balance, at Sep. 30, 2014	$ 336,375	$ 5,173	30,139	297,454	3,983	(374)
Shares Issued, Beginning Balance (in shares) at Dec. 31, 2014	5,173,450	5,173,000
Balance, at Dec. 31, 2014	$ 348,399	$ 5,173	30,139	299,004	14,457	(374)
Net income	53,335			53,335
Dividends paid	(53,675)			(53,675)
Change in unrealized net gain on available-for-sale securities	(3,527)				(3,527)
Change in value of interest rate cap	(8)				(8)
Deferred stock unit grants	$ 600		600
Shares Issued, Ending Balance (in shares) at Sep. 30, 2015	5,173,450	5,173,000
Balance, at Sep. 30, 2015	$ 345,124	$ 5,173	$ 30,739	$ 298,664	$ 10,922	$ (374)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 53,335	$ 49,764
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization, including amortization of debt issuance costs	24,725	23,838
Straight-lining of rental income	(1,276)	(1,905)
Stock-based compensation expense	600	394
Reversal of income tax liability	0	(420)
Change in operating assets and liabilities:
Tenant and other receivables, net	(559)	538
Other assets	(13,969)	(14,345)
Amounts due to Vornado	(102)	872
Accounts payable and accrued expenses	9,527	7,686
Other liabilities	(23)	(13)
Net cash provided by operating activities	72,258	66,409
CASH FLOWS FROM INVESTING ACTIVITIES
Construction in progress and real estate additions	(41,919)	(39,957)
Change in restricted cash	(168)	5,294
Proceeds from maturing short-term investments	24,998	0
Net cash used in investing activities	(17,089)	(34,663)
CASH FLOWS FROM FINANCING ACTIVITIES
Debt repayments	(322,372)	(316,418)
Proceeds from borrowing	350,000	300,000
Dividends paid	(53,675)	(49,825)
Debt issuance costs	(4,071)	(4,245)
Net cash used in financing activities	(30,118)	(70,488)
Net increase (decrease) in cash and cash equivalents	25,051	(38,742)
Cash and cash equivalents at beginning of period	227,815	347,718
Cash and cash equivalents at end of period	252,866	308,976
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash payments for interest, excluding capitalized interest of $1,420 and $265 respectively	18,065	24,062
NON-CASH TRANSACTIONS
Liability for real estate additions (including $5,540 due to Vornado in 2015)	13,259	14,296
Write-off of fully amortized and/or depreciated assets	$ 9,600	$ 10,569

Consolidated Statements of Cash Flows (Parentheticals) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash paid for interest, capitalized	$ 1,420	$ 265
Non Cash Additions To Real Estate	13,259	$ 14,296
Vornado [Member]
Non Cash Additions To Real Estate	$ 5,540

Organization

9 Months Ended

Sep. 30, 2015

Organization and Basis of Presentation [Abstract]

Organization [Text Block]

1. Organization

Alexander's, Inc. (NYSE: ALX) is a real estate investment trust (“REIT”), incorporated in Delaware, engaged in leasing, managing, developing and redeveloping its properties. All references to “we,” “us,” “our,” “Company” and “Alexander's” refer to Alexander's, Inc. and its consolidated subsidiaries. We are managed by, and our properties are leased and developed by, Vornado Realty Trust (“Vornado”) (NYSE: VNO).

Basis of Presentation

9 Months Ended

Sep. 30, 2015

Organization and Basis of Presentation [Abstract]

Basis of Presentation [Text Block]

2. Basis of Presentation

The accompanying consolidated financial statements are unaudited and include the accounts of Alexander's and its consolidated subsidiaries. All intercompany amounts have been eliminated. In our opinion, all adjustments (which include only normal recurring adjustments) necessary to present fairly the financial position, results of operations and changes in cash flows have been made. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted. These condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q of the Securities and Exchange Commission (the “SEC”) and should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014, as filed with the SEC.

We have made estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for the three and nine months ended September 30, 2015 are not necessarily indicative of the operating results for the full year.

We currently operate in one business segment.

Significant Accounting Policy

9 Months Ended

Sep. 30, 2015

Significant Accounting Policy [Abstract]

Significant Accounting Policy [Text Block]

3. Significant Accounting Policy

Development and Construction in Progress – We are constructing an apartment tower, The Alexander, above our Rego Park II shopping center, containing 312 units aggregating 255,000 square feet. The estimated cost of this project, including initial leasing costs to achieve stabilized occupancy, is approximately $125,000,000, of which $113,000,000 has been incurred as of September 30, 2015. We capitalize all property operating expenses directly associated with and attributable to, the development and construction of a project, including interest expense. The capitalization period begins when development activities are underway and ends when it is determined that the asset is substantially complete and ready for its intended use, which is typically evidenced by the receipt of a temporary certificate of occupancy (“TCO”). In the third quarter of 2015, we received a TCO for certain floors of the apartment tower where construction has been substantially completed. Accordingly, this portion of the apartment tower has been placed in service. Construction of the remaining floors is expected to be substantially completed during the fourth quarter of 2015 and we expect to receive the related TCO by December 31, 2015.

Recently Issued Accounting Literature

9 Months Ended

Sep. 30, 2015

Recently Issued Accounting Literature [Abstract]

Recently Issued Accounting Literature [Text Block]

4. Recently Issued Accounting Literature

In April 2014, the Financial Accounting Standards Board (“FASB”) issued an update (“ASU 2014-08”) Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity to Accounting Standards Codification (“ASC”) Topic 205, Presentation of Financial Statements and ASC Topic 360, Property Plant and Equipment. Under ASU 2014-08, only disposals that represent a strategic shift that has (or will have) a major effect on the entity's results and operations qualify as discontinued operations. In addition, ASU 2014-08 expands the disclosure requirements for disposals that meet the definition of a discontinued operation and requires entities to disclose information about disposals of individually significant components that do not meet the definition of discontinued operations. ASU 2014-08 was effective for interim and annual reporting periods in fiscal years that begin after December 15, 2014. The adoption of this update on January 1, 2015 did not have any impact on our consolidated financial statements.

In May 2014, the FASB issued an update (“ASU 2014-09”) establishing ASC Topic 606 Revenue from Contracts with Customers. ASU 2014-09 establishes a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most of the existing revenue recognition guidance. ASU 2014-09 requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services and also requires certain additional disclosures. ASU 2014-09 is effective for interim and annual reporting periods in fiscal years that begin after December 15, 2017. We are currently evaluating the impact of the adoption of ASU 2014-09 on our consolidated financial statements.

In April 2015, the FASB issued an update (“ASU 2015-03”) Simplifying the Presentation of Debt Issuance Costs to ASC Topic 835, Interest. ASU 2015-03 requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the debt liability to which they relate, consistent with debt discounts, as opposed to being presented as assets. ASU 2015-03 is effective for interim and annual reporting periods in fiscal years that begin after December 15, 2015. The adoption of this update on January 1, 2016 will not have a material impact on our consolidated financial statements.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6510796

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=28359718&loc=d3e22583-107794

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Indirect Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6515603

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28359718&loc=d3e22580-107794

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.10-01.(b)(6))
-URI http://asc.fasb.org/extlink&oid=27015980&loc=d3e46468-122699

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accounting Change
-URI http://asc.fasb.org/extlink&oid=6503790

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=28359718&loc=d3e22499-107794

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Retrospective Application
-URI http://asc.fasb.org/extlink&oid=6523989

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=6372559&loc=d3e765-108305

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=6372559&loc=d3e725-108305

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 01
-Paragraph b
-Subparagraph 6
-Article 10

+ Details

Relationship with Vornado

9 Months Ended

Sep. 30, 2015

Relationship with Vornado [Abstract]

Relationship with Vornado [Text Block]

5. Relationship with Vornado

As of September 30, 2015, Vornado owned 32.4% of our outstanding common stock. We are managed by, and our properties are leased and developed by, Vornado, pursuant to the agreements described below, which expire in March of each year and are automatically renewable.

Management and Development Agreements

We pay Vornado an annual management fee equal to the sum of (i) $2,800,000, (ii) 2% of gross revenue from the Rego Park II shopping center, (iii) $0.50 per square foot of the tenant-occupied office and retail space at 731 Lexington Avenue and (iv) $280,000, escalating at 3% per annum, for managing the common area of 731 Lexington Avenue. Vornado is also entitled to a development fee equal to 6% of development costs, as defined.

Leasing Agreements

Vornado also provides us with leasing services for a fee of 3% of rent for the first ten years of a lease term, 2% of rent for the eleventh through the twentieth year of a lease term, and 1% of rent for the twenty-first through thirtieth year of a lease term, subject to the payment of rents by tenants. In the event third-party real estate brokers are used, the fees to Vornado increase by 1% and Vornado is responsible for the fees to the third-party real estate brokers. Vornado is also entitled to a commission upon the sale of any of our assets equal to 3% of gross proceeds, as defined, for asset sales less than $50,000,000 and 1% of gross proceeds, as defined, for asset sales of $50,000,000 or more. Prior to December 22, 2014, the total of these amounts was payable in annual installments in an amount not to exceed $4,000,000, with interest on the unpaid balance at one-year LIBOR plus 1.0%. On December 22, 2014, the leasing agreements with Vornado were amended to eliminate the annual installment cap of $4,000,000 and we paid the accrued balance of leasing commissions of $40,353,000 to Vornado.

Other Agreements

We also have agreements with Building Maintenance Services, a wholly owned subsidiary of Vornado, to supervise (i) cleaning, engineering and security services at our 731 Lexington Avenue property and (ii) security services at our Rego Park I and Rego Park II properties, for an annual fee equal to the cost of such services plus 6%.

The following is a summary of fees to Vornado under the various agreements discussed above.


5. Relationship with Vornado - continued
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(Amounts in thousands)		2015		2014		2015		2014
	Company management fees		$	700	$	700	$	2,100	$	2,100
	Development fees			517		1,714		2,176		2,463
	Leasing fees			21		911		419		1,275
	Property management fees and payments for cleaning, engineering
		and security services		838		1,012		2,621		2,723
			$	2,076	$	4,337	$	7,316	$	8,561

As of September 30, 2015, the amounts due to Vornado were $5,540,000 for development fees; $411,000 for management, property management, cleaning and security fees; and $15,000 for leasing fees. As of December 31, 2014, the amounts due to Vornado were $3,394,000 for development fees and $528,000 for management, property management and cleaning fees.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Marketable Securities

9 Months Ended

Sep. 30, 2015

Marketable Securities [Abstract]

Marketable Securities [Text Block]

6. Marketable Securities

As of September 30, 2015 and December 31, 2014, we owned 535,265 common shares of The Macerich Company (“Macerich”) (NYSE: MAC), which were received in connection with the sale of the Kings Plaza Regional Shopping Center (“Kings Plaza”) to Macerich in November 2012. These shares have an economic cost of $56.05 per share, or $30,000,000 in the aggregate. As of September 30, 2015 and December 31, 2014, the fair value of these shares was $41,119,000 and $44,646,000, respectively, based on Macerich's closing share price of $76.82 per share and $83.41 per share, respectively. These shares are included in “marketable securities” on our consolidated balance sheets and are classified as available-for-sale. Available-for-sale securities are presented at fair value and unrealized gains and losses resulting from the mark-to-market of these securities are included in “other comprehensive income.”

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Significant Tenants

9 Months Ended

Sep. 30, 2015

Significant Tenants [Abstract]

Significant Tenants [Text Block]

7. Significant Tenants

Bloomberg L.P. (“Bloomberg”) accounted for revenue of $70,702,000 and $67,488,000, representing approximately 45% of our total revenues in each of the nine-month periods ended September 30, 2015 and 2014, respectively. No other tenant accounted for more than 10% of our total revenues. If we were to lose Bloomberg as a tenant, or if Bloomberg were to be unable to fulfill its obligations under its lease, it would adversely affect our results of operations and financial condition. In order to assist us in our continuing assessment of Bloomberg's creditworthiness, we receive certain confidential financial information and metrics from Bloomberg. In addition, we access and evaluate financial information regarding Bloomberg from other private sources, as well as publicly available data.

In October 2014, Bloomberg exercised its option to extend leases that were scheduled to expire in December 2015 covering 188,608 square feet of office space at our 731 Lexington Avenue property for a term of five years. We are currently in negotiations with Bloomberg to determine the rental rate for the extension period.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2015

Stock-Based Compensation [Abstract]

Stock-Based Compensation [Text Block]

8. Stock-Based Compensation

We account for stock-based compensation in accordance with ASC 718, Compensation – Stock Compensation. Our Omnibus Stock Plan provides for grants of incentive and non-qualified stock options, restricted stock, stock appreciation rights, deferred stock units (“DSUs”) and performance shares, as defined, to the directors, officers and employees of the Company and Vornado.

In May 2015, we granted each of the members of our Board of Directors 176 DSUs with a grant date fair value of $56,250 per grant, or $450,000 in the aggregate. In addition, 468 DSUs, constituting an initial award with a grant date fair value of $150,000, were granted to a newly appointed Director. The DSUs entitle the holders to receive shares of the Company's common stock without the payment of any consideration. The DSUs vested immediately and accordingly, were expensed on the date of grant, but the shares of common stock underlying the DSUs are not deliverable to the grantee until the grantee is no longer serving on the Company's Board of Directors.

Mortgages Payable

9 Months Ended

Sep. 30, 2015

Mortgages Payable [Abstract]

Mortgages Payable [Text Block]

9. Mortgages Payable

On August 5, 2015, we completed a $350,000,000 refinancing of the retail portion of 731 Lexington Avenue. The interest-only loan is at LIBOR plus 1.40% and matures in August 2020, with two one-year extension options.

The following is a summary of our outstanding mortgages payable as of September 30, 2015 and December 31, 2014.

					Balance at
			Interest Rate at		September 30,			December 31,
(Amounts in thousands)		Maturity⁽¹⁾	September 30, 2015		2015			2014
First mortgages secured by:
	Rego Park I shopping center (100% cash
	collateralized)⁽²⁾	Mar. 2016	0.40	%	$	78,246		$	78,246
	Paramus	Oct. 2018	2.90	%		68,000			68,000
	Rego Park II shopping center⁽³⁾	Nov. 2018	2.04	%		264,162			266,534
	731 Lexington Avenue, office space⁽⁴⁾	Mar. 2021	1.16	%		300,000			300,000
	731 Lexington Avenue, retail space	Aug. 2022	1.61	%		350,000	⁽⁵⁾		320,000
					$	1,060,408		$	1,032,780

(1)	Represents the extended maturity where we have the unilateral right to extend.
(2)	Extended for one year from March 10, 2015.
(3)	Interest at LIBOR plus 1.85%.
(4)	Interest at LIBOR plus 0.95%.
(5)	Interest at LIBOR plus 1.40%.

Fair Value Measurements

9 Months Ended

Sep. 30, 2015

Fair Value Measurements [Abstract]

Fair Value Measurements [Text Block]

10. Fair Value Measurements

ASC 820, Fair Value Measurements and Disclosures defines fair value and establishes a framework for measuring fair value. ASC 820 establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three levels: Level 1 – quoted prices (unadjusted) in active markets that are accessible at the measurement date for assets or liabilities; Level 2 – observable prices that are based on inputs not quoted in active markets, but corroborated by market data; and Level 3 – unobservable inputs that are used when little or no market data is available. The fair value hierarchy gives the highest priority to Level 1 inputs and the lowest priority to Level 3 inputs. In determining fair value, we utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible, as well as consider counterparty credit risk in our assessment of fair value.

Financial Assets and Liabilities Measured at Fair Value

Financial assets measured at fair value on our consolidated balance sheets as of September 30, 2015 and December 31, 2014, consist of marketable securities, short-term investments (treasury bills classified as available-for-sale) and an interest rate cap, which are presented in the table below, based on their level in the fair value hierarchy. There were no financial liabilities measured at fair value as of September 30, 2015 and December 31, 2014.


10. Fair Value Measurements - continued

				As of September 30, 2015
	(Amounts in thousands)			Total		Level 1		Level 2		Level 3
		Marketable securities		$	41,119	$	41,119	$	-	$	-
			Total assets	$	41,119	$	41,119	$	-	$	-

				As of December 31, 2014
	(Amounts in thousands)			Total		Level 1		Level 2		Level 3
		Marketable securities		$	44,646	$	44,646	$	-	$	-
		Short-term investments			24,998		24,998		-		-
		Interest rate cap (included in other assets)			11		-		11		-
			Total assets	$	69,655	$	69,644	$	11	$	-

Financial Assets and Liabilities not Measured at Fair Value

Financial assets and liabilities that are not measured at fair value on our consolidated balance sheets include cash equivalents, mortgages payable and leasing commissions due to Vornado. Cash equivalents are carried at cost, which approximates fair value due to their short-term maturities. The fair value of our mortgages payable is calculated by discounting the future contractual cash flows of these instruments using current risk-adjusted rates available to borrowers with similar credit ratings, which are provided by a third-party specialist. The leasing commissions due to Vornado are carried at cost plus interest at variable rates, which approximate fair value. The fair value of cash equivalents is classified as Level 1 and the fair values of mortgages payable and leasing commissions due to Vornado are classified as Level 2. The table below summarizes the carrying amounts and fair value of these financial instruments as of September 30, 2015 and December 31, 2014.

		As of September 30, 2015				As of December 31, 2014
		Carrying		Fair		Carrying		Fair
(Amounts in thousands)		Amount		Value		Amount		Value
Assets:
	Cash equivalents	$	221,539	$	221,539	$	111,590	$	111,590

Liabilities:
	Mortgages payable	$	1,060,408	$	1,054,200	$	1,032,780	$	1,025,000
	Leasing commissions (included in amounts due to Vornado)		15		15		-		-
		$	1,060,423	$	1,054,215	$	1,032,780	$	1,025,000

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Commitments and Contingencies

9 Months Ended

Sep. 30, 2015

Commitments and Contingencies [Abstract]

Commitments and Contingencies [Text Block]

11. Commitments and Contingencies

Insurance

We maintain general liability insurance with limits of $300,000,000 per occurrence and all-risk property and rental value insurance coverage with limits of $1.7 billion per occurrence, including coverage for acts of terrorism, with sub-limits for certain perils such as floods and earthquakes on each of our properties.

Fifty Ninth Street Insurance Company, LLC (“FNSIC”), our wholly owned consolidated subsidiary, acts as a direct insurer for coverage for acts of terrorism, including nuclear, biological, chemical and radiological (“NBCR”) acts, as defined by the Terrorism Risk Insurance Program Reauthorization Act, which expires in December 2020. Coverage for acts of terrorism (including NBCR acts) is up to $1.7 billion per occurrence and in the aggregate. Coverage for acts of terrorism (excluding NBCR acts) is fully reinsured by third party insurance companies with no exposure to FNSIC. For NBCR acts, FNSIC is responsible for a $275,000 deductible and 15% of the balance (16% effective January 1, 2016) of a covered loss, and the Federal government is responsible for the remaining 85% (84% effective January 1, 2016) of a covered loss. We are ultimately responsible for any loss incurred by FNSIC.

We continue to monitor the state of the insurance market and the scope and costs of coverage for acts of terrorism. However, we cannot anticipate what coverage will be available on commercially reasonable terms in the future. We are responsible for deductibles and losses in excess of our insurance coverage, which could be material.

Our mortgage loans are non-recourse to us and contain customary covenants requiring us to maintain insurance. Although we believe that we have adequate insurance coverage for purposes of these agreements, we may not be able to obtain an equivalent amount of coverage at reasonable costs in the future. If lenders insist on greater coverage than we are able to obtain, it could adversely affect our ability to finance our properties.

Rego Park I Litigation

On June 24, 2014, Sears Roebuck and Co. (“Sears”) filed a lawsuit in the Supreme Court of the State of New York against Vornado and us (and certain of our subsidiaries) with regard to space that Sears leases at our Rego Park I property. Sears alleges that the defendants are liable for harm that Sears has suffered as a result of (a) water intrusions into the premises, (b) two fires in February 2014 that caused damages to those premises, and (c) alleged violations of the Americans with Disabilities Act in the premises' parking garage. Sears asserts various causes of actions for damages and seeks to compel compliance with landlord's obligations to repair the premises and to provide security, and to compel us to abate a nuisance that Sears claims was a cause of the water intrusions into its premises. In addition to injunctive relief, Sears seeks, among other things, damages of not less than $4 million and future damages it estimates will not be less than $25 million. We intend to defend the claims vigorously. The amount or range of reasonably possible losses, if any, cannot be estimated.

Paramus

In 2001, we leased 30.3 acres of land located in Paramus, New Jersey to IKEA Property, Inc. The lease has a purchase option in 2021 for $75,000,000. The property is encumbered by a $68,000,000 interest-only mortgage loan with a fixed rate of 2.90%, which matures in October 2018. The annual triple-net rent is the sum of $700,000 plus the amount of debt service on the mortgage loan. If the purchase option is exercised, we will receive net cash proceeds of approximately $7,000,000 and recognize a gain on sale of land of approximately $60,000,000. If the purchase option is not exercised, the triple-net rent for the last 20 years would include debt service sufficient to fully amortize $68,000,000 over the remaining 20-year lease term.

Letters of Credit

Approximately $2,074,000 of standby letters of credit were outstanding as of September 30, 2015.

Other

On October 15, 2015, the New York City Department of Finance (“NYC DOF”) issued a Notice of Determination to us assessing an additional $20,300,000 of transfer taxes (including interest and penalties) in connection with the sale of Kings Plaza in November 2012. We believe that the NYC DOF's claim is without merit and intend to vigorously contest this assessment. We have determined that the likelihood of a loss related to this issue is not probable and, after consultation with legal counsel, that the outcome of this assessment is not expected to have a material adverse effect on our financial position, results of operations or cash flows.

There are various other legal actions against us in the ordinary course of business. In our opinion, the outcome of such matters in the aggregate will not have a material effect on our financial position, results of operations or cash flows.

Earnings Per Share

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

Earnings Per Share [Text Block]

12. Earnings Per Share

The following table sets forth the computation of basic and diluted income per share, including a reconciliation of net income and the number of shares used in computing basic and diluted income per share. Basic income per share is determined using the weighted average shares of common stock outstanding during the period. Diluted income per share is determined using the weighted average shares of common stock outstanding during the period, and assumes all potentially dilutive securities were converted into common shares at the earliest date possible. There were no potentially dilutive securities outstanding during the three and nine months ended September 30, 2015 and 2014.

		Three Months Ended				Nine Months Ended
		September 30,				September 30,
(Amounts in thousands, except share and per share amounts)		2015		2014		2015		2014
	Net income	$	18,172	$	17,692	$	53,335	$	49,764

	Weighted average shares outstanding – basic and diluted		5,113,077		5,111,201		5,112,108		5,110,435

	Net income per common share – basic and diluted	$	3.55	$	3.46	$	10.43	$	9.74

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2015
Significant Accounting Policy [Abstract]
Basis of Accounting [Policy Text Block]	The accompanying consolidated financial statements are unaudited and include the accounts of Alexander's and its consolidated subsidiaries. All intercompany amounts have been eliminated. In our opinion, all adjustments (which include only normal recurring adjustments) necessary to present fairly the financial position, results of operations and changes in cash flows have been made. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted. These condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q of the Securities and Exchange Commission (the “SEC”) and should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014, as filed with the SEC. We have made estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for the three and nine months ended September 30, 2015 are not necessarily indicative of the operating results for the full year. We currently operate in one business segment.
Recently Issued Accounting Literature [Policy Text Block]	In April 2014, the Financial Accounting Standards Board (“FASB”) issued an update (“ASU 2014-08”) Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity to Accounting Standards Codification (“ASC”) Topic 205, Presentation of Financial Statements and ASC Topic 360, Property Plant and Equipment. Under ASU 2014-08, only disposals that represent a strategic shift that has (or will have) a major effect on the entity's results and operations qualify as discontinued operations. In addition, ASU 2014-08 expands the disclosure requirements for disposals that meet the definition of a discontinued operation and requires entities to disclose information about disposals of individually significant components that do not meet the definition of discontinued operations. ASU 2014-08 was effective for interim and annual reporting periods in fiscal years that begin after December 15, 2014. The adoption of this update on January 1, 2015 did not have any impact on our consolidated financial statements. In May 2014, the FASB issued an update (“ASU 2014-09”) establishing ASC Topic 606 Revenue from Contracts with Customers. ASU 2014-09 establishes a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most of the existing revenue recognition guidance. ASU 2014-09 requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services and also requires certain additional disclosures. ASU 2014-09 is effective for interim and annual reporting periods in fiscal years that begin after December 15, 2017. We are currently evaluating the impact of the adoption of ASU 2014-09 on our consolidated financial statements. In April 2015, the FASB issued an update (“ASU 2015-03”) Simplifying the Presentation of Debt Issuance Costs to ASC Topic 835, Interest. ASU 2015-03 requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the debt liability to which they relate, consistent with debt discounts, as opposed to being presented as assets. ASU 2015-03 is effective for interim and annual reporting periods in fiscal years that begin after December 15, 2015. The adoption of this update on January 1, 2016 will not have a material impact on our consolidated financial statements.
Marketable Securities, Available-for-sale Securities, Policy [Policy Text Block]	Available-for-sale securities are presented at fair value and unrealized gains and losses resulting from the mark-to-market of these securities are included in “other comprehensive income.”
Fair Value Measurement Policy [Policy Text Block]	In determining fair value, we utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible, as well as consider counterparty credit risk in our assessment of fair value.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	We account for stock-based compensation in accordance with ASC 718, Compensation – Stock Compensation. Our Omnibus Stock Plan provides for grants of incentive and non-qualified stock options, restricted stock, stock appreciation rights, deferred stock units (“DSUs”) and performance shares, as defined, to the directors, officers and employees of the Company and Vornado.
Real Estate [Policy Text Block]	Development and Construction in Progress – We are constructing an apartment tower, The Alexander, above our Rego Park II shopping center, containing 312 units aggregating 255,000 square feet. The estimated cost of this project, including initial leasing costs to achieve stabilized occupancy, is approximately $125,000,000, of which $113,000,000 has been incurred as of September 30, 2015. We capitalize all property operating expenses directly associated with and attributable to, the development and construction of a project, including interest expense. The capitalization period begins when development activities are underway and ends when it is determined that the asset is substantially complete and ready for its intended use, which is typically evidenced by the receipt of a temporary certificate of occupancy (“TCO”). In the third quarter of 2015, we received a TCO for certain floors of the apartment tower where construction has been substantially completed. Accordingly, this portion of the apartment tower has been placed in service. Construction of the remaining floors is expected to be substantially completed during the fourth quarter of 2015 and we expect to receive the related TCO by December 31, 2015.

Relationship with Vornado (Tables)

9 Months Ended

Sep. 30, 2015

Relationship with Vornado [Abstract]

Summary of Fees to Vornado [Table Text Block]


5. Relationship with Vornado - continued
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(Amounts in thousands)		2015		2014		2015		2014
	Company management fees		$	700	$	700	$	2,100	$	2,100
	Development fees			517		1,714		2,176		2,463
	Leasing fees			21		911		419		1,275
	Property management fees and payments for cleaning, engineering
		and security services		838		1,012		2,621		2,723
			$	2,076	$	4,337	$	7,316	$	8,561

Mortgages Payable (Tables)

9 Months Ended

Sep. 30, 2015

Mortgages Payable [Abstract]

Summary of Notes and Mortgages Payable [Table Text Block]

					Balance at
			Interest Rate at		September 30,			December 31,
(Amounts in thousands)		Maturity⁽¹⁾	September 30, 2015		2015			2014
First mortgages secured by:
	Rego Park I shopping center (100% cash
	collateralized)⁽²⁾	Mar. 2016	0.40	%	$	78,246		$	78,246
	Paramus	Oct. 2018	2.90	%		68,000			68,000
	Rego Park II shopping center⁽³⁾	Nov. 2018	2.04	%		264,162			266,534
	731 Lexington Avenue, office space⁽⁴⁾	Mar. 2021	1.16	%		300,000			300,000
	731 Lexington Avenue, retail space	Aug. 2022	1.61	%		350,000	⁽⁵⁾		320,000
					$	1,060,408		$	1,032,780

(1)	Represents the extended maturity where we have the unilateral right to extend.
(2)	Extended for one year from March 10, 2015.
(3)	Interest at LIBOR plus 1.85%.
(4)	Interest at LIBOR plus 0.95%.
(5)	Interest at LIBOR plus 1.40%.

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value Measurements [Abstract]

Fair Value, Assets Measured on Recurring Basis [Table Text Block]


10. Fair Value Measurements - continued

				As of September 30, 2015
	(Amounts in thousands)			Total		Level 1		Level 2		Level 3
		Marketable securities		$	41,119	$	41,119	$	-	$	-
			Total assets	$	41,119	$	41,119	$	-	$	-

				As of December 31, 2014
	(Amounts in thousands)			Total		Level 1		Level 2		Level 3
		Marketable securities		$	44,646	$	44,646	$	-	$	-
		Short-term investments			24,998		24,998		-		-
		Interest rate cap (included in other assets)			11		-		11		-
			Total assets	$	69,655	$	69,644	$	11	$	-

Fair Value, by Balance Sheet Grouping [Table Text Block]

		As of September 30, 2015				As of December 31, 2014
		Carrying		Fair		Carrying		Fair
(Amounts in thousands)		Amount		Value		Amount		Value
Assets:
	Cash equivalents	$	221,539	$	221,539	$	111,590	$	111,590

Liabilities:
	Mortgages payable	$	1,060,408	$	1,054,200	$	1,032,780	$	1,025,000
	Leasing commissions (included in amounts due to Vornado)		15		15		-		-
		$	1,060,423	$	1,054,215	$	1,032,780	$	1,025,000

Earnings Per Share (Tables)

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

		Three Months Ended				Nine Months Ended
		September 30,				September 30,
(Amounts in thousands, except share and per share amounts)		2015		2014		2015		2014
	Net income	$	18,172	$	17,692	$	53,335	$	49,764

	Weighted average shares outstanding – basic and diluted		5,113,077		5,111,201		5,112,108		5,110,435

	Net income per common share – basic and diluted	$	3.55	$	3.46	$	10.43	$	9.74

Basis of Presentation (Details)	9 Months Ended
Basis of Presentation (Details)	Sep. 30, 2015 Segment
Organization and Basis of Presentation [Abstract]
Number Of Operating Segments	1

Significant Accounting Policy (Details) ft² in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) ft² aptunits	Dec. 31, 2014 USD ($)
Real Estate Properties [Line Items]
Development and construction in progress	$ 40,189	$ 75,289
Rego Park II [Member] \| Property Under Development [Member] \| Apartment Tower [Member]
Real Estate Properties [Line Items]
Number of units in real estate property (in units) \| aptunits	312
Area of property (in square feet) \| ft²	255
Estimated Budgeted Cost	$ 125,000
Development and construction in progress	$ 113,000
Estimated Date Of Completion	Fourth quarter of 2015

Relationship with Vornado (Details) - Vornado [Member]		3 Months Ended		9 Months Ended
Relationship with Vornado (Details) - Vornado [Member]	Dec. 22, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) $ / ft²	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent		32.40%		32.40%
Management and Development Agreements
Management Fee Agreement Value (in US dollars)				$ 2,800,000
Leasing Agreement [Abstract]
Asset Sale Commission Threshold (in US dollars)				$ 50,000,000
Percentage Commissions On Sale Of Assets Under Fifty Million				3.00%
Percentage Commissions On Sale Of Assets Over Fifty Million				1.00%
Leasing services fee and commission on asset sale, annual installment, maximum. (in US dollars)	$ 4,000,000
Debt Instrument, Description of Variable Rate Basis	One-year LIBOR
Basis spread over LIBOR	1.00%
Repayment of leasing costs (in US Dollars)	$ 40,353,000
Summary of fees to Vornado
Fees to related party (in US dollars)		$ 2,076,000	$ 4,337,000	$ 7,316,000	$ 8,561,000
Lexington Avenue Property [Member]
Other Agreements [Abstract]
Other Supervisory Fees				6.00%
Lexington Avenue Property [Member] \| Office And Retail Space [Member]
Management and Development Agreements
Property Management Fee Agreement Price Per Square Foot \| $ / ft²				0.5
Lexington Avenue Property [Member] \| Common Area [Member]
Management and Development Agreements
Property Management Fee Agreement Value (in US dollars)				$ 280,000
Property Management Fee Escalation Percentage Per Annum				3.00%
Rego Park I [Member]
Other Agreements [Abstract]
Security Services Fee				6.00%
Rego Park II [Member]
Management and Development Agreements
Property Management Fee Agreement Percentage Of Income				2.00%
Other Agreements [Abstract]
Security Services Fee				6.00%
Company Management Fees [Member]
Summary of fees to Vornado
Fees to related party (in US dollars)		700,000	700,000	$ 2,100,000	2,100,000
Development fees [Member]
Management and Development Agreements
Development fee as percentage of development costs				6.00%
Summary of fees to Vornado
Fees to related party (in US dollars)		517,000	1,714,000	$ 2,176,000	2,463,000
Fees owed to Vornado (in US dollars)		5,540,000		$ 5,540,000		$ 3,394,000
Leasing Fees [Member]
Leasing Agreement [Abstract]
Lease Fee Percentage Of Rent One To Ten Years				3.00%
Lease Fee Percentage Of Rent Eleven To Twenty Years				2.00%
Lease Fee Percentage Of Rent Twenty First To Thirty Years				1.00%
Percentage Increase Lease Fee If Broker Used				1.00%
Summary of fees to Vornado
Fees to related party (in US dollars)		21,000	911,000	$ 419,000	1,275,000
Fees owed to Vornado (in US dollars)		15,000		15,000
Property Management Fees [Member]
Summary of fees to Vornado
Fees to related party (in US dollars)		838,000	$ 1,012,000	2,621,000	$ 2,723,000
Fees owed to Vornado (in US dollars)		$ 411,000		$ 411,000		$ 528,000

Marketable Securities (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment Holdings [Line Items]
Fair Value	$ 41,119	$ 44,646
Macerich interest [Member]
Investment Holdings [Line Items]
Macerich Common Shares	535,265	535,265
Economic basis per share (in dollars per share)	$ 56.05
GAAP Cost	$ 30,000
Fair Value	$ 41,119	$ 44,646
Closing share price (in dollars per share)	$ 76.82	$ 83.41

Significant Tenants (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
Significant Tenants (Details) $ in Thousands	Oct. 31, 2014 ft²	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Real Estate Properties [Line Items]
Real estate revenue, net (in dollars)		$ 52,414	$ 50,077	$ 155,096	$ 149,528
Bloomberg [Member]
Real Estate Properties [Line Items]
Leases Expiration Date	December 2015
Bloomberg [Member] \| 731 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Square Footage of Real Estate Property (in square feet) \| ft²	188,608
Lease renewal term	5 years
Bloomberg [Member] \| Customer Concentration Risk [Member]
Real Estate Properties [Line Items]
Percentage Of Minimum Revenue Threshold Contributed By One Tenant (in percentage)				10.00%
Bloomberg [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Services Net [Member]
Real Estate Properties [Line Items]
Real estate revenue, net (in dollars)				$ 70,702	$ 67,488
Percentage Rent Contributed By Tenant				45.00%	45.00%

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	May 31, 2015	Jun. 30, 2015	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized in connection with the issuance of Deferred Stock Units (in US dollars)			$ 600	$ 394
Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Granted Per Director (in shares)	176
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Grant Date Fair Value, Granted Per Director	$ 56,250
Expense recognized in connection with the issuance of Deferred Stock Units (in US dollars)	$ 450
Deferred Stock Units [Member] \| Newly Appointed Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Granted Per Director (in shares)		468
Expense recognized in connection with the issuance of Deferred Stock Units (in US dollars)		$ 150

Mortgages Payable (Details)		9 Months Ended
Mortgages Payable (Details)	Aug. 05, 2015 USD ($) extensionoptions	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Mortgage Loans on Real Estate [Line Items]
Notes Payable (in US dollars)		$ 1,060,408,000	$ 1,032,780,000
Rego Park 1 Shopping [Member] \| Mortgages [Member] \| Secured [Member]
Mortgage Loans on Real Estate [Line Items]
Notes Payable (in US dollars)		$ 78,246,000	78,246,000
Maturity date		2016-03
Percentage of cash mortgage collateralized		100.00%
Interest rate (in percentage)		0.40%
Duration Of Mortgage Loan Extension		1 year
Rego Park 2 Property [Member] \| Mortgages [Member] \| Secured [Member]
Mortgage Loans on Real Estate [Line Items]
Notes Payable (in US dollars)		$ 264,162,000	266,534,000
Basis spread over LIBOR (in percentage)		1.85%
Maturity date		2018-11
Interest rate (in percentage)		2.04%
Lexington Avenue Property [Member] \| Mortgages [Member] \| Secured [Member] \| Office Space [Member]
Mortgage Loans on Real Estate [Line Items]
Notes Payable (in US dollars)		$ 300,000,000	300,000,000
Basis spread over LIBOR (in percentage)		0.95%
Maturity date		2021-03
Interest rate (in percentage)		1.16%
Lexington Avenue Property [Member] \| Mortgages [Member] \| Secured [Member] \| Retail Space [Member]
Mortgage Loans on Real Estate [Line Items]
Notes Payable (in US dollars)	$ 350,000,000	$ 350,000,000	320,000,000
Debt Instrument, Description of Variable Rate Basis	LIBOR
Basis spread over LIBOR (in percentage)	1.40%	1.40%
Maturity date	August 2020	2022-08
Number Of Extensions Available \| extensionoptions	2
Term of extension available	1 year
Interest rate (in percentage)		1.61%
Paramus Property [Member] \| Mortgages [Member] \| Secured [Member]
Mortgage Loans on Real Estate [Line Items]
Notes Payable (in US dollars)		$ 68,000,000	$ 68,000,000
Maturity date		2018-10
Interest rate (in percentage)		2.90%

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 41,119	$ 44,646
Short-term Investments	0	24,998
Interest rate cap (included in other assets)		11
Total assets	41,119	69,655
Liabilities measured at fair value	0	0
Carrying Reported Amount Fair Value Disclosure [Member]
Assets
Cash Equivalents	221,539	111,590
Liabilities
Mortgages Payable	1,060,408	1,032,780
Leasing commissions (included in amounts due to Vornado)	15	0
Total liabilities not measured at fair value	1,060,423	1,032,780
Estimate Of Fair Value Fair Value Disclosure [Member]
Assets
Cash Equivalents	221,539	111,590
Liabilities
Mortgages Payable	1,054,200	1,025,000
Leasing commissions (included in amounts due to Vornado)	15	0
Total liabilities not measured at fair value	1,054,215	1,025,000
Fair Value, Inputs, Level 1 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	41,119	44,646
Short-term Investments		24,998
Interest rate cap (included in other assets)		0
Total assets	41,119	69,644
Fair Value, Inputs, Level 2 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Short-term Investments		0
Interest rate cap (included in other assets)		11
Total assets	0	11
Fair Value, Inputs, Level 3 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Short-term Investments		0
Interest rate cap (included in other assets)		0
Total assets	$ 0	$ 0

Commitments and Contingencies (Details)			9 Months Ended	12 Months Ended
Commitments and Contingencies (Details)	Oct. 15, 2015 USD ($)	Jun. 24, 2014 USD ($) Fires	Sep. 30, 2015 USD ($)	Dec. 31, 2021 USD ($)	Jan. 01, 2016	Dec. 31, 2014 USD ($)	Dec. 31, 2001 a
Paramus Property [Abstract]
Mortgages payable			$ 1,060,408,000			$ 1,032,780,000
Letters Of Credit [Abstract]
Standby letters of credit, outstanding			2,074,000
Kings Plaza Regional Shopping Center [Member] \| Subsequent Event [Member]
Loss Contingency [Abstract]
Loss Contingency, claim value	$ 20,300,000
Paramus Property [Member] \| Tenant Occupant [Member] \| Ikea [Member]
Paramus Property [Abstract]
Area Of Land (in acre) \| a							30.3
Mortgages payable			$ 68,000,000
Fixed interest rate on the debt (in percentage)			2.90%
Debt Instrument Maturity Date String			October 2018
Triple-net rent, annual amount			$ 700,000
Paramus Property [Member] \| Tenant Occupant [Member] \| Ikea [Member] \| Scenario Forecast [Member]
Paramus Property [Abstract]
Property purchase option exercisable be leasee with purchase option in 2021				$ 75,000,000
Purchase option exercised, net cash proceeds from sale of land				7,000,000
Purchase option excercised, gain on sale of land				60,000,000
Purchase option not excercised amount included in triple net rent over remainder of lease				$ 68,000,000
Loan Amortization Period				20 years
Rego Park I [Member] \| Sears [Member]
Loss Contingency [Abstract]
Number Of Fires \| Fires		2
Rego Park I [Member] \| Sears [Member] \| Minimum [Member]
Loss Contingency [Abstract]
Loss Contingency, claim value		$ 4,000,000
Rego Park I [Member] \| Sears [Member] \| Minimum [Member] \| Estimated Future Damages [Member]
Loss Contingency [Abstract]
Loss Contingency, claim value		$ 25,000,000
General Liability [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident			300,000,000
All Risk Property And Rental Value [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident			1,700,000,000
Terrorism Coverage Including Nbcr [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident			1,700,000,000
Insurance Maximum Coverage In Aggregate			$ 1,700,000,000
NBCR [Member]
Insurance [Abstract]
Insurance Coverage End Date			December 2020
Deductible			$ 275,000
Self Insured Responsibility (in percentage)			15.00%
Federal Government Responsibility (in percentage)			85.00%
NBCR [Member] \| Scenario Forecast [Member]
Insurance [Abstract]
Self Insured Responsibility (in percentage)					16.00%
Federal Government Responsibility (in percentage)					84.00%

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 18,172	$ 17,692	$ 53,335	$ 49,764
Weighted average shares outstanding- basic and diluted (in shares)	5,113,077	5,111,201	5,112,108	5,110,435
Net income per common share- basic and diluted (in dollars per share)	$ 3.55	$ 3.46	$ 10.43	$ 9.74

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details