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Mortgages and Other Loans Payable (Details) | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Feb. 24, 2020 USD ($) | Jan. 31, 2020 USD ($) | Aug. 31, 2019 extension | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2019 USD ($) extension | Dec. 31, 2018 USD ($) | Apr. 30, 2018 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total fixed rate debt |  |  |  |  |  | $ 1,383,449,000 | $ 1,389,717,000 |
Total floating rate debt |  |  |  |  |  | 828,434,000 | 598,442,000 |
Total mortgages and other loans payable |  |  |  |  |  | 2,211,883,000 | 1,988,159,000 |
Deferred financing costs, net of amortization |  |  |  |  |  | (28,630,000) | (26,919,000) |
Total mortgages and other loans payable |  |  |  |  |  | 2,183,253,000 | 1,961,240,000 |
Book value of collateral |  |  |  |  |  | 3,300,000,000 | 2,600,000,000 |
Outstanding under line of credit facility |  |  |  |  |  | 234,013,000 | 492,196,000 |
FHLB Facility January 2020 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 10,000,000 | 0 |
FHLB Facility January 2020 | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 0.26% |  |
FHLB Facility February 2020 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 15,000,000 | 0 |
FHLB Facility February 2020 | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 0.32% |  |
FHLB Facility June 2020 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 14,500,000 | 0 |
FHLB Facility June 2020 | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 0.17% |  |
2017 Master Repurchase Agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 152,684,000 | 300,000,000 |
Maximum facility capacity |  |  |  |  |  | 300,000,000.0 |  | $ 400,000,000.0
Number of extension options | extension |  |  | 2 |  |  |  |  |
Number of extension option |  |  | 1 year | 1 year | 1 year |  |  |
Outstanding under line of credit facility |  |  |  |  |  | $ 152,400,000 |  |
2017 Master Repurchase Agreement | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 2.19% |  |
FHLB Facility, August 2019 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  |  | 13,000,000 |
FHLB Facility, December 2019 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  |  | 14,500,000 |
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 |  |  |  |  |  | $ 209,296,000 | 213,208,000 |
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 |  |  |  |  |  | $ 299,165,000 | 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 |  |  |  |  |  | $ 39,094,000 | 39,931,000 |
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 |  |  |  |  |  | $ 35,123,000 | 35,807,000 |
1080 Amsterdam Avenue | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, fixed rate debt (as a percent) |  |  |  |  |  | 3.59% |  |
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% |  |
A133 Greene Street |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 15,523,000 | 15,523,000 |
A133 Greene Street | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 2.00% |  |
106 Spring Street |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 38,025,000 | 0 |
106 Spring Street | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 2.50% |  |
609 Fifth Avenue |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 53,773,000 | 0 |
609 Fifth Avenue | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 2.40% |  |
185 Broadway |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 120,110,000 | 111,869,000 |
185 Broadway | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 2.85% |  |
712 Madison Avenue |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 28,000,000 | 28,000,000 |
712 Madison Avenue | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 1.85% |  |
410 Tenth Avenue |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 330,819,000 | 0 |
410 Tenth Avenue | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 2.23% |  |
719 Seventh Avenue |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  | $ 50,000,000 | 50,000,000 |
719 Seventh Avenue | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, floating rate debt (as a percent) |  |  |  |  |  | 1.20% |  |
1080 Amsterdam |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total fixed rate debt |  |  |  |  |  | $ 34,200,000 |  |
Subordinate loan |  |  |  |  |  | $ 900,000 |  |
1080 Amsterdam | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Term (in Years) |  |  |  |  |  | 5 years |  |
1080 Amsterdam | Mortgage loan | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, fixed rate debt (as a percent) |  |  |  |  |  | 3.50% |  |
1080 Amsterdam | Senior Subordinated Loans | Weighted Average |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate, fixed rate debt (as a percent) |  |  |  |  |  | 7.00% |  |
115 Spring Street |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total floating rate debt |  |  |  |  |  |  | $ 65,550,000 |
Construction Loans | 185 Broadway |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Term (in Years) |  |  |  |  |  | 3 years |  |
Maximum facility capacity |  |  |  |  |  | $ 225,000,000.0 |  |
Number of extension options | extension |  |  |  |  |  | 2 |  |
Period of extension option |  |  |  |  |  | 1 year |  |
Construction Loans | 410 Tenth Avenue |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Maximum facility capacity |  |  |  |  |  | $ 465.0 |  |
Number of extension options | extension |  |  |  |  |  | 2 |  |
Construction Loans | 460 West 34th Street |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Term (in Years) |  |  |  |  |  | 3 years |  |
Period of extension option |  |  |  |  |  | 1 year |  |
LIBOR Plus 25 Basis Points | Ticonderoga |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
FHLB advances |  |  |  |  |  | $ 39,500,000 |  |
LIBOR Plus 25 Basis Points | Ticonderoga | LIBOR |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate added to base rate (as a percent) |  |  |  |  |  | 0.25% |  |
115 Spring Street |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Ownership percentage in disposed asset |  |  | 49.00% |  |  | 49.00% |  |
Deconsolidation of ownership interest percentage |  |  | 51.00% |  |  | 51.00% |  |
Subsequent Event | FHLB Facility January 2020 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Face amount of loan |  | $ 10,000,000.0 |  |  |  |  |  |
Interest rate added to base rate (as a percent) |  | 0.165% |  |  |  |  |  |
Subsequent Event | FHLB Facility February 2020 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Face amount of loan | $ 15,000,000.0 |  |  |  |  |  |  |
Interest rate added to base rate (as a percent) | 0.26% |  |  |  |  |  |  |

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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 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 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959 + 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://fasb.org/us-gaap/role/ref/legacyRef -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://fasb.org/us-gaap/role/ref/legacyRef -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 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 + Details
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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 Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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