Debt Instrument, Number of Extension Options

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- Definition

Debt Instrument, Number of Instruments

+ References

No definition available.

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- Definition

Debt Instrument, Period of Extension Option

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- Definition

Line of Credit Facility, Basis Point Fee

+ References

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- Definition

Line of Credit Facility, Threshold Amount for Basis Point Fee

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- Definition

Secured Debt, Amount Transferred to Liabilities Related to Net Assets Held for Sale

+ References

No definition available.

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- Definition

Represents the carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations and other loans payable.

+ References

No definition available.

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- Definition

The portion of the carrying amount of long-term secured loans outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

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- Definition

Secured Debt, Bearing Fixed Interest, Mortgage Amount

+ References

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- Definition

Secured Debt, Bearing Fixed Interest, Subordinate Loan Amount

+ References

No definition available.

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- Definition

The portion of the carrying amount of long-term secured loans outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ References

No definition available.

+ Details

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- Definition

Secured Debt, Deferred Finance Costs, Net

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- Definition

Secured Debt, Gross

+ References

No definition available.

+ Details

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624258-113959

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ 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 944
-SubTopic 210
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

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- Definition

As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
-Subparagraph (12)(c)
-URI http://asc.fasb.org/extlink&oid=65877616&loc=SL6540498-122764

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
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-URI http://asc.fasb.org/extlink&oid=65877616&loc=SL6540498-122764

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=65877616&loc=SL6540498-122764

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
-Subparagraph 14
-URI http://asc.fasb.org/extlink&oid=65877616&loc=SL6540498-122764

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

The per share liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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Mortgages and Other Loans Payable (Details)	3 Months Ended
Mortgages and Other Loans Payable (Details)	Mar. 31, 2018 USD ($) extension debt_instrument $ / shares	Apr. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)
Debt Instrument [Line Items]
Total fixed rate debt	$ 1,891,154,000		$ 2,400,560,000
Total floating rate debt	565,026,000		465,431,000
Total fixed rate and floating rate debt	2,456,180,000		2,865,991,000
Mortgages reclassed to liabilities related to assets held for sale	0		0
Total mortgages and other loans payable	2,456,180,000		2,865,991,000
Deferred financing costs, net of amortization	(22,186,000)		(28,709,000)
Total mortgages and other loans payable, net	2,433,994,000		2,837,282,000
Book value of collateral	3,500,000,000		4,800,000,000
Outstanding under line of credit facility	0		30,336,000
Series J Preferred Units
Debt Instrument [Line Items]
Total fixed rate debt	4,000,000		4,000,000
Limited partnership interest	$ 4,000,000
Preferred units (as a percent)	3.75%
Preferred units, liquidation preference (in dollars per unit) \| $ / shares	$ 1,000.00
Series J Preferred Units \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.75%
Unsecured Loan
Debt Instrument [Line Items]
Total fixed rate debt	$ 16,000,000		16,000,000
Unsecured Loan \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.81%
Uncommitted Master Repurchase Agreements
Debt Instrument [Line Items]
Number of debt instruments \| debt_instrument	2
Uncommitted Master Repurchase Agreement 2017
Debt Instrument [Line Items]
Total floating rate debt	$ 189,883,000		90,809,000
Term (in Years)	1 year
Maximum facility capacity	$ 300,000,000.0
Number of extension options \| extension	2
Period of extension options	1 year
Outstanding under line of credit facility	$ 189,500,000
Uncommitted Master Repurchase Agreement 2017 \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.23%
Uncommitted Master Repurchase Agreement 2016
Debt Instrument [Line Items]
Term (in Years)	2 years
Maximum facility capacity				$ 300,000,000.0
Period of extension options	1 year
Basis point fee (as a percent)	0.25%
Outstanding under line of credit facility	$ (600,000)
Threshold amount for basis point fee to be applicable (less than)	$ 150,000,000.0
Uncommitted Master Repurchase Agreement 2016 \| Minimum \| LIBOR
Debt Instrument [Line Items]
Credit facility, interest rate (as a percent)	2.25%
Uncommitted Master Repurchase Agreement 2016 \| Maximum \| LIBOR
Debt Instrument [Line Items]
Credit facility, interest rate (as a percent)	4.00%
One Madison Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 477,843,000		486,153,000
One Madison Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	5.91%
762 Madison Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 771,000		771,000
762 Madison Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	5.00%
100 Church Street
Debt Instrument [Line Items]
Total fixed rate debt	$ 216,240,000		217,273,000
100 Church Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.68%
420 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 300,000,000		300,000,000
420 Lexington Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.99%
400 East 58th Street
Debt Instrument [Line Items]
Total fixed rate debt	$ 40,000,000		40,000,000
400 East 58th Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.00%
Term (in Years)	5 years
Landmark Square
Debt Instrument [Line Items]
Total fixed rate debt	$ 100,000,000		100,000,000
Landmark Square \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.90%
485 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 450,000,000		450,000,000
485 Lexington Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.25%
1080 Amsterdam Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 36,300,000		36,363,000
Total fixed rate debt	35,500,000
Subordinate loan	$ 900,000
1080 Amsterdam Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.58%
Term (in Years)	5 years
1080 Amsterdam Avenue \| Mortgage loan \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.50%
1080 Amsterdam Avenue \| Subordinate loan \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	7.00%
315 West 33rd Street
Debt Instrument [Line Items]
Total fixed rate debt	$ 250,000,000		250,000,000
315 West 33rd Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.17%
919 Third Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 0		500,000,000
919 Third Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)
719 Seventh Avenue
Debt Instrument [Line Items]
Total floating rate debt	$ 42,143,000		41,622,000
719 Seventh Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	3.05%
183, 187 Broadway & 5-7 Dey Street
Debt Instrument [Line Items]
Total floating rate debt	$ 58,000,000		58,000,000
183, 187 Broadway & 5-7 Dey Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.70%
220 East 42nd Street
Debt Instrument [Line Items]
Total floating rate debt	$ 275,000,000		$ 275,000,000
220 East 42nd Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	1.60%
Subsequent Event \| Uncommitted Master Repurchase Agreement 2017
Debt Instrument [Line Items]
Maximum facility capacity		$ 400,000,000.0