Reckson Operating Partnership 10-Q 13 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 13, 2018
Document and Entity Information
Entity Registrant Name	RECKSON OPERATING PARTNERSHIP LP
Entity Central Index Key	930,810
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		0
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commercial real estate properties, at cost:
Land and land interests	$ 1,274,981	$ 1,704,142
Building and improvements	3,196,383	4,251,610
Building leasehold and improvements	1,073,703	1,073,703
Commercial real estate properties, gross	5,545,067	7,029,455
Less: accumulated depreciation	(1,279,827)	(1,492,603)
Total commercial real estate properties, net	4,265,240	5,536,852
Assets held for sale	0	67,228
Cash and cash equivalents	35,608	36,013
Restricted cash	39,570	41,117
Tenant and other receivables, net of allowance of $7,138 and $7,237 in 2018 and 2017, respectively	20,540	31,006
Deferred rents receivable, net of allowance of $9,553 and $11,189 in 2018 and 2017, respectively	181,900	233,300
Debt and preferred equity investments, net of discounts and deferred origination fees of $16,973 and $25,507 in 2018 and 2017, respectively	1,977,057	2,114,041
Investments in unconsolidated joint ventures	477,686	130,217
Deferred costs, net of accumulated amortization of $81,131 and $77,176 in 2018 and 2017, respectively	76,907	106,136
Other assets	230,040	245,598
Total assets	7,304,548	8,541,508
Liabilities
Mortgages and other loans payable, net	607,061	829,648
Unsecured term loan, net	651,340	901,067
Accrued interest payable	8,067	14,999
Other liabilities	58,231	92,514
Accounts payable and accrued expenses	50,534	60,819
Related party payables	0	23,808
Deferred revenue	28,666	134,650
Deferred land leases payable	1,958	1,888
Dividends payable	807	807
Security deposits	38,142	39,085
Liabilities related to assets held for sale	0	42
Total liabilities	1,444,806	2,099,327
Commitments and contingencies
Preferred units	109,161	109,161
Capital
General partner capital	5,725,638	6,012,134
Limited partner capital	0	0
Accumulated other comprehensive loss	0	(1,259)
Total ROP partner's capital	5,725,638	6,010,875
Noncontrolling interests in other partnerships	24,943	322,145
Total capital	5,750,581	6,333,020
Total liabilities and capital	$ 7,304,548	$ 8,541,508

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Tenant and other receivables, net of allowance of $7,138 and $7,237 in 2018 and 2017, respectively	$ 7,138	$ 7,237
Deferred rents receivable, net of allowance of $9,553 and $11,189 in 2018 and 2017, respectively	9,553	11,189
Debt and preferred equity investments, net of discounts and deferred origination fees of $16,973 and $25,507 in 2018 and 2017, respectively	16,973	25,507
Deferred costs, net of accumulated amortization of $81,131 and $77,176 in 2018 and 2017, respectively	81,131	77,176
Land and land interests	1,274,981	1,704,142
Building and improvements	3,196,383	4,251,610
Accumulated depreciation	1,279,827	1,492,603
Other assets	230,040	245,598
Real estate debt, net	607,061	829,648
Accrued interest payable	8,067	14,999
Other liabilities	58,231	92,514
Variable Interest Entity
Land and land interests	45,100	268,600
Building and improvements	200,000	1,300,000
Accumulated depreciation	20,700	319,100
Other assets	624,000	143,900
Real estate debt, net	0	495,000
Accrued interest payable	0	2,100
Other liabilities	$ 9,400	$ 48,800

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Rental revenue, net	$ 128,726	$ 167,346	$ 401,846	$ 502,376
Escalation and reimbursement	20,492	25,721	60,400	73,163
Investment income	49,125	47,946	143,087	148,924
Other income	244	895	10,531	1,612
Total revenues	198,587	241,908	615,864	726,075
Expenses
Operating expenses, including related party expenses of $6,021 and $18,178 in 2018, and $6,922 and $20,099 in 2017, respectively.	32,049	43,448	99,412	123,938
Real estate taxes	33,500	40,610	98,045	118,232
Ground rent	4,759	5,236	15,068	15,706
Interest expense, net of interest income	15,458	34,627	47,818	96,202
Amortization of deferred financing costs	721	2,580	3,777	6,706
Depreciation and amortization	41,867	53,549	125,163	156,106
Transaction related costs	2	0	283	2
Marketing, general and administrative	131	92	405	321
Total expenses	128,487	180,142	389,971	517,213
Equity in net (loss) income from unconsolidated joint ventures	(164)	2,927	3,835	10,362
(Loss) gain on sale of real estate	(2,773)	114	(17,636)	5,047
Depreciable real estate reserves	0	(379)	0	(85,707)
Purchase price and other fair value adjustments	0	0	54,860	0
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	6,345	282	5,982	285
Net income	73,508	64,710	272,934	138,849
Net (income) loss attributable to noncontrolling interests in other partnerships	(212)	1,467	(716)	19,587
Preferred units distributions	(955)	(955)	(2,865)	(2,863)
Net income attributable to ROP common unitholder	$ 72,341	$ 65,222	$ 269,353	$ 155,573

Consolidated Statements of Op_2

Consolidated Statements of Operations (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Related party expenses included in operating expenses	$ 6,021	$ 6,922	$ 18,178	$ 20,099

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income attributable to ROP common unitholder	$ 72,341	$ 65,222	$ 269,353	$ 155,573
Other comprehensive income:
Change in net unrealized gain on derivative instruments	0	89	0	269
Comprehensive income attributable to ROP common unitholder	$ 72,341	$ 65,311	$ 269,353	$ 155,842

Consolidated Statement of Capit

Consolidated Statement of Capital (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Partners' Capital
Beginning Balance	$ 5,805,073	$ 5,244,364	$ 6,333,020	$ 5,528,823
Contributions	505,210	546,482	1,114,901	1,913,792
Distributions	(632,255)	(771,506)	(1,543,224)	(2,270,662)
Deconsolidation of partially owned entity	0	0	(297,140)	0
Net income	72,553	63,755	197,516	72,231
Other comprehensive income	0	89	0	180
Ending Balance	5,750,581	5,083,184	5,805,073	5,244,364
General Partner's Capital Class A Common Units | Class A Common Units
Increase (Decrease) in Partners' Capital
Beginning Balance	5,780,209	4,873,544	6,012,134	5,139,842
Contributions	505,210	546,482	1,113,642	1,913,792
Distributions	(632,122)	(727,833)	(1,542,579)	(2,270,441)
Net income	72,341	65,222	197,012	90,351
Ending Balance	5,725,638	4,757,415	5,780,209	4,873,544
Limited Partner's Capital
Increase (Decrease) in Partners' Capital
Beginning Balance	0	0	0	0
Ending Balance	0	0	0	0
Noncontrolling Interests In Other Partnerships
Increase (Decrease) in Partners' Capital
Beginning Balance	24,864	372,258	322,145	390,599
Distributions	(133)	(43,673)	(645)	(221)
Deconsolidation of partially owned entity	0	0	(297,140)	0
Net income	212	(1,467)	504	(18,120)
Ending Balance	24,943	327,118	24,864	372,258
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Partners' Capital
Beginning Balance	0	(1,438)	(1,259)	(1,618)
Contributions	0	0	1,259	0
Other comprehensive income	0	89	0	180
Ending Balance	$ 0	$ (1,349)	$ 0	$ (1,438)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities
Net income	$ 272,934	$ 138,849
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	128,940	162,812
Equity in net income from unconsolidated joint ventures	(3,835)	(10,362)
Distributions of cumulative earnings from unconsolidated joint ventures	3,850	12,032
Equity in net gain on sale of interest in unconsolidated joint venture interest/real estate	(5,982)	(285)
Purchase price and other fair value adjustments	(54,860)	0
Loss (gain) on sale of real estate	17,636	(5,047)
Depreciable real estate reserves	0	85,707
Deferred rents receivable	4,372	(9,063)
Other non-cash adjustments	(30,017)	(33,917)
Changes in operating assets and liabilities:
Tenant and other receivables	389	(625)
Deferred lease costs	(12,733)	(9,589)
Other assets	(35,840)	(51,792)
Accounts payable, accrued expenses, other liabilities and security deposits	(1,173)	(2,460)
Deferred revenue and land leases payable	8,891	9,356
Net cash provided by operating activities	292,572	285,616
Investing Activities
Acquisitions of real estate properties	224	0
Additions to land, buildings and improvements	(82,959)	(98,460)
Investments in unconsolidated joint ventures	(20,449)	(84)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	114,178	49,038
Net proceeds from disposition of real estate/joint venture interest	243,488	157,251
Other investments	(16,328)	57,785
Origination of debt and preferred equity investments	(652,309)	(935,724)
Repayments or redemption of debt and preferred equity investments	542,623	677,676
Net cash provided by (used in) investing activities	128,468	(92,518)
Financing Activities
Proceeds from mortgages and other loans payable	274,741	250,000
Proceeds from revolving credit facility and senior unsecured notes	0	1,447,800
Repayments of revolving credit facility and senior unsecured notes	(250,000)	(1,167,800)
Distributions to noncontrolling interests in other partnerships	(778)	(43,894)
Contributions from common unitholder	1,461,354	2,321,970
Distributions to common and preferred unitholders	(1,904,482)	(3,001,084)
Other obligations related to loan participations	109	16,737
Deferred loan costs and capitalized lease obligation	(3,936)	(4,481)
Net cash used in financing activities	(422,992)	(180,752)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(1,952)	12,346
Cash, cash equivalents, and restricted cash at beginning of year	77,130	103,419
Cash, cash equivalents, and restricted cash at end of period	75,178	115,765
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Tenant improvements and capital expenditures payable	9,112	6,447
Transfer of assets related to assets held for sale	0	273,455
Transfer of liabilities related to assets held for sale	0	1,290
Removal of fully depreciated commercial real estate properties	14,220	3,955
Contributions from common unitholder	157,498	138,304
Distributions to common unitholder	273,084	0
Deconsolidation of a subsidiary	280,718	3,520
Cash and cash equivalents	35,608	36,014
Total cash, cash equivalents, and restricted cash	$ 77,130	$ 103,419

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Reckson Operating Partnership, L.P., or ROP, commenced operations on June 2, 1995. The sole general partner of ROP is Wyoming Acquisition GP LLC., or WAGP, a wholly-owned subsidiary of SL Green Operating Partnership, L.P., or the Operating Partnership. The sole limited partner of ROP is the Operating Partnership. The Operating Partnership is 94.90% owned by SL Green Realty Corp., or SL Green, as of September 30, 2018 . SL Green is a self-administered and self-managed real estate investment trust, and is the sole managing general partner of the Operating Partnership. Unless the context requires otherwise, all references to "we," "our," "us" and the "Company" means ROP and all entities owned or controlled by ROP. We are engaged in the acquisition, ownership, management and operation of commercial and residential real estate properties, principally office properties, and also own land for future development in the New York metropolitan area. As of September 30, 2018 , we owned the following interests in properties in the New York metropolitan area, primarily in midtown Manhattan. Our investments located outside of Manhattan are referred to as the Suburban properties: Location Type Number of Approximate Square Feet (unaudited) Weighted Average (1) (unaudited) Commercial: Manhattan Office (2)(3) 15 8,303,245 93.6 % Retail (4)(5) 5 364,816 98.9 % Development/Redevelopment 1 160,000 — % 21 8,828,061 92.2 % Suburban Office 6 1,432,400 93.8 % Retail 1 52,000 100.0 % 7 1,484,400 94.0 % Total commercial properties 28 10,312,461 92.4 % Residential: Manhattan Residential (4) — 222,855 95.8 % Total portfolio 28 10,535,316 92.5 % (1) The weighted average occupancy for commercial properties represents the total occupied square feet divided by total square footage at acquisition. The weighted average occupancy for residential properties represents the total occupied units divided by total available units. (2) Includes one unconsolidated joint venture property at 919 Third Avenue comprised of approximately 1,454,000 square feet. (3) Includes one unconsolidated tenancy-in-common (or "TIC") interest at 2 Herald Square, which is under contract for sale as of September 30, 2018 . (4) As of September 30, 2018 , we owned a building at 315 West 33rd Street, also known as The Olivia, that was comprised of approximately 270,132 square feet (unaudited) of retail space and approximately 222,855 square feet (unaudited) of residential space. For the purpose of this report, we have included this building in the number of retail properties we own. However, we have included only the retail square footage in the retail approximate square footage, and have listed the balance of the square footage as residential square footage. (5) Includes two unconsolidated joint venture retail properties at 131-137 Spring Street comprised of approximately 68,342 square feet. As of September 30, 2018 , we held debt and preferred equity investments with a book value of $2.0 billion . Basis of Quarterly Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by accounting principles generally accepted in the United States for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for the fair presentation of the financial position of the Company at September 30, 2018 and the results of operations for the periods presented have been included. The operating results for the period presented are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Annual Report on Form 10-K for the year ended December 31, 2017 . The consolidated balance sheet at December 31, 2017 has been derived from the audited financial statements as of that date but does not include all the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Principles of Consolidation The consolidated financial statements include our accounts and those of our subsidiaries, which are wholly-owned or controlled by us. Entities which we do not control through our voting interest and entities which are variable interest entities, but where we are not the primary beneficiary, are accounted for under the equity method. See Note 5, "Debt and Preferred Equity Investments" and Note 6, "Investments in Unconsolidated Joint Ventures." All significant intercompany balances and transactions have been eliminated. We consolidate a VIE in which we are considered the primary beneficiary. The primary beneficiary is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. Investment in Commercial Real Estate Properties We allocate the purchase price of real estate to land and building (inclusive of tenant improvements) and, if determined to be material, intangibles, such as the value of above- and below-market leases and origination costs associated with the in-place leases. We depreciate the amount allocated to building (inclusive of tenant improvements) over their estimated useful lives, which generally range from three to 40 years . We amortize the amount allocated to the above- and below-market leases over the remaining term of the associated lease, which generally range from one to 14 years , and record it as either an increase (in the case of below-market leases) or a decrease (in the case of above-market leases) to rental income. We amortize the amount allocated to the values associated with in-place leases over the expected term of the associated lease, which generally ranges from one to 14 years . If a tenant vacates its space prior to the contractual termination of the lease and no rental payments are being made on the lease, any unamortized balance of the related intangible will be written off. The tenant improvements and origination costs are amortized as an expense over the remaining life of the lease (or charged against earnings if the lease is terminated prior to its contractual expiration date). We assess fair value of the leases based on estimated cash flow projections that utilize appropriate discount and capitalization rates and available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known trends, and market/economic conditions that may affect the property. To the extent acquired leases contain fixed rate renewal options that are below-market and determined to be material, we amortize such below-market lease value into rental income over the renewal period. On a periodic basis, we assess whether there are any indications that the value of our real estate properties may be other than temporarily impaired or that their carrying value may not be recoverable. A property's value is considered impaired if management's estimate of the aggregate future cash flows (undiscounted) to be generated by the property is less than the carrying value of the property. To the extent impairment has occurred, the loss will be measured as the excess of the carrying amount of the property over the calculated fair value of the property. We also evaluate our real estate properties for impairment when a property has been classified as held for sale. Real estate assets held for sale are valued at the lower of their carrying value or fair value less costs to sell. We recognized $1.3 million and $5.5 million of rental revenue for the three and nine months ended September 30, 2018 , respectively, and $4.3 million and $12.7 million for the three and nine months ended September 30, 2017 , respectively, for the amortization of aggregate below-market leases in excess of above-market leases and a reduction in lease origination costs, resulting from the allocation of the purchase price of the applicable properties. The following summarizes our identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases) as of September 30, 2018 and December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Identified intangible assets (included in other assets): Gross amount $ 213,421 $ 276,163 Accumulated amortization (199,668 ) (236,737 ) Net (1) $ 13,753 $ 39,426 Identified intangible liabilities (included in deferred revenue): Gross amount $ 230,275 $ 496,438 Accumulated amortization (214,804 ) (366,091 ) Net (1) $ 15,471 $ 130,347 (1) As of September 30, 2018 and December 31, 2017 , $0.0 million and $0.1 million , respectively and $0.0 million and $0.1 million , respectively, of net intangible assets and net intangible liabilities, were reclassified to assets held for sale and liabilities related to assets held for sale. Fair Value Measurements See Note 12, "Fair Value Measurements." Investments in Unconsolidated Joint Ventures We assess our investments in unconsolidated joint ventures for recoverability, and if it is determined that a loss in value of the investment is other than temporary, we write down the investment to its fair value. We evaluate our equity investments for impairment based on the joint ventures' projected discounted cash flows. We do not believe that the values of any of our equity investments were impaired at September 30, 2018 . Reserve for Possible Credit Losses The reserve for possible credit losses in connection with debt and preferred equity investments is the charge to earnings to increase the allowance for possible credit losses to the level that we estimate to be adequate, based on Level 3 data, considering delinquencies, loss experience and collateral quality. Other factors considered include geographic trends, product diversification, the size of the portfolio and current economic conditions. Based upon these factors, we establish a provision for possible credit loss on each individual investment. When it is probable that we will be unable to collect all amounts contractually due, the investment is considered impaired. Where impairment is indicated on an investment that is held to maturity, a valuation allowance is measured based upon the excess of the recorded investment amount over the fair value of the collateral. Any deficiency between the carrying amount of an asset and the calculated value of the collateral is charged to expense. We continue to assess or adjust our estimates based on circumstances of a loan and the underlying collateral. If additional information reflects increased recovery of our investment, we will adjust our reserves accordingly. There were no loan reserves recorded during the three and nine months ended September 30, 2018 and 2017 . Debt and preferred equity investments held for sale are carried at the lower of cost or fair market value using available market information obtained through consultation with dealers or other originators of such investments as well as discounted cash flow models based on Level 3 data pursuant to ASC 820-10. As circumstances change, management may conclude not to sell an investment designated as held for sale. In such situations, the investment will be reclassified at its net carrying value to debt and preferred equity investments held to maturity. For these reclassified investments, the difference between the current carrying value and the expected cash to be collected at maturity will be accreted into income over the remaining term of the investment. Income Taxes ROP is a disregarded entity of SL Green Operating Partnership, L.P. for federal income tax purposes, and, as a result, all income and losses of ROP are considered income and losses of SL Green Operating Partnership, L. P. No provision has been made for income taxes in the consolidated financial statements since such taxes, if any, are the responsibility of the individual partners of SL Green Operating Partnership, L.P. Shares Contributed by Parent Company We present shares of SL Green common stock as a contra-equity account within general partner capital in our consolidated financial statements. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Concentrations of Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash investments, debt and preferred equity investments and accounts receivable. We place our cash investments with high quality financial institutions. The collateral securing our debt and preferred equity investments is located in the New York metropolitan area. See Note 5, "Debt and Preferred Equity Investments." We perform ongoing credit evaluations of our tenants and require most tenants to provide security deposits or letters of credit. Though these security deposits and letters of credit are insufficient to meet the total value of a tenant's lease obligation, they are a measure of good faith and a source of funds to offset the economic costs associated with lost revenue and the costs associated with re-tenanting a space. The properties in our real estate portfolio are located in the New York metropolitan area. The tenants located in our buildings operate in various industries. No tenant in our portfolio accounted for more than 5.0% of our share of annualized cash rent, including our share of joint venture annualized rent, at September 30, 2018 . For the three months ended September 30, 2018 , 14.7% , 11.0% , 8.7% , 8.4% , 8.2% , 7.6% , 7.4% , 7.1% and 5.8% of our annualized cash rent was attributable to 1185 Avenue of the Americas, 625 Madison Avenue, 919 Third Avenue, 750 Third Avenue, 810 Seventh Avenue, 555 West 57th Street, 125 Park Avenue, 1350 Avenue of the Americas, and 711 Third Avenue, respectively. Annualized cash rent for all other properties was below 5.0% . Reclassification Certain prior year balances have been reclassified to conform to our current year presentation. Accounting Standards Updates In August 2018, The Securities and Exchange Commission adopted a final rule that eliminated or amended disclosure requirements that were redundant or outdated in light of changes in its requirements, generally accepted accounting principles, or changes in the business environment. The commission also referred certain disclosure requirements to the Financial Accounting Standards Board for potential incorporation into generally accepted accounting principles. The Company assessed the impact of this rule and determined that the changes resulted in clarification or expansion of existing requirements. The Company adopted the rule on November 5, 2018 and it did not have a material impact on the Company’s consolidated financial statements. In August 2018, the FASB issued Accounting Standard Update (ASU) No. 2018-15, Intangibles - Goodwill and Other- Internal-Use Software (Topic 350-40), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. The amendments provide guidance on accounting for fees paid when the arrangement includes a software license and align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing costs to develop or obtain internal-use software. The guidance will be effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted. The Company has not yet adopted this new guidance and does not expect it to have a material impact on the Company’s consolidated financial statements when the new standard is implemented. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This amendment removed, modified and added the disclosure requirements under Topic 820. The changes are effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted for the removed or modified disclosures with adoption of the additional disclosures upon the effective date. The Company has not yet adopted this new guidance and does not expect it to have a material impact on the Company’s consolidated financial statements when the new standard is implemented. In February 2018, the FASB issued ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments- Overall (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. These amendments provide additional guidance related to equity securities without a readily determinable fair value, forward contracts and options purchased on those equity securities and fair value option liabilities. The Company adopted the guidance on July 1, 2018, and it did not have a material impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities, and in July 2018, the FASB issued ASU No. 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The amendments in the new standards will permit more flexibility in hedging interest rate risk for both variable rate and fixed rate financial instruments. The standards will also enhance the presentation of hedge results in the financial statements. The guidance is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company has not yet adopted the guidance, and does not expect a material impact on the Company’s consolidated financial statements when the new standards are implemented. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The guidance requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash. As a result, entities will no longer present transfers between these items on the statement of cash flows. The Company adopted the guidance on January 1, 2018 and has included the changes in restricted cash when reconciling the beginning-of-period and end-of-period total amounts on the statement of cash flows. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The guidance changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current ‘incurred loss’ model with an ‘expected loss’ approach. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 15, 2018. The Company has not yet adopted this new guidance and is currently evaluating the impact of adopting this new accounting standard on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases, and in July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements. This guidance requires lessees to recognize lease assets and lease liabilities for those leases classified as operating leases under the previous standard. Depending on the lease classification, lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The accounting applied by a lessor, inclusive of the effect of a practical expedient offered in ASU No. 2018-11 that allows lessors to not separate non-lease components from the related lease components under certain conditions, which the Company expects most of its leases to qualify for and to adopt, is largely unchanged from that applied under the previous standard. However, the Company will apply this guidance to the ground leases under which the Company is lessee. The Company is required to record a liability for the obligation to make payments under the lease and an asset for the right to use the underlying asset during the lease term and will also apply the new expense recognition requirements given the lease classification. While the Company is continuing to assess all potential impacts of the standard, we expect total liabilities and total assets to increase by $0.1 to $0.2 billion as of the date of adoption. This guidance is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The Company expects to adopt this guidance January 1, 2019 and will apply the modified retrospective approach, and anticipates electing the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classification for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. In January 2016, the FASB issued ASU 2016-01 (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. The guidance requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value through earnings, to record changes in instrument-specific credit risk for financial liabilities measured under the fair value option in other comprehensive income, use the exit price notion when measuring an instrument’s fair value for disclosure and to separately present financial assets and liabilities by measurement category and form of instrument on the balance sheet or in the notes to the financial statements. The Company adopted the guidance effective January 1, 2018, and it had no impact on the Company’s consolidated financial statements. In May 2014, the FASB issued a new comprehensive revenue recognition guidance which requires us to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods and services (ASU 2014-09). The FASB also issued implementation guidance in March 2016, April 2016 and May 2016 - ASU’s 2016-08, 2016-10 and 2016-12, respectively. The Company adopted this guidance on January 1, 2018. Since the Company’s revenue is related to leasing activities, the adoption of this guidance did not have a material impact on the consolidated financial statements. The new guidance is applicable to service contracts with joint ventures for which the Company earns property management fees, leasing commissions and development and construction fees. The adoption of this new guidance did not change the accounting for these fees as the pattern of recognition of revenue does not change with the new guidance. We will continue to recognize revenue over time on these contracts because the customer simultaneously receives and consumes the benefits provided by our performance. In February 2017, the FASB issued ASU No. 2017-05 to clarify the scope of asset derecognition guidance in Subtopic 610-20, which also provided guidance on accounting for partial sales of nonfinancial assets. Subtopic 610-20 was issued in May 2014 as part of ASU 2014-09. The Company adopted this guidance on January 1, 2018, and applied the modified retrospective approach. The Company elected to adopt the practical expedient under ASC 606, Revenue from Contracts with Customers, which allows an entity to apply the guidance only to contracts with non-customers that are open based on ASU 360-20, Real Estate Sales, (i.e. failed sales) as of the adoption date. The adoption had no impact on the consolidated financial statements as the Company had no open contracts based on ASC 360-20 as of December 31, 2017 .

Property Acquisitions

Property Acquisitions	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Property Acquisitions	Property Acquisitions During the nine months ended September 30, 2018 , we did not acquire any properties from a third party.

Properties Held for Sale and Pr

Properties Held for Sale and Property Dispositions	9 Months Ended
	Sep. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Properties Held for Sale and Property Dispositions	Properties Held for Sale and Property Dispositions Properties Held for Sale As of September 30, 2018 , no properties were classified as held for sale. Property Dispositions The following table summarizes the properties sold during the nine months ended September 30, 2018 : Property Disposition Date Property Type Approximate Square Feet Sales Price (1) (in millions) Gain (loss) (2) (in millions) 115-117 Stevens Avenue May 2018 Fee Interest 178,000 $ 12.0 $ (0.7 ) 635 Madison Avenue June 2018 Fee Interest 176,530 153.0 (14.1 ) 1-6 International Drive July 2018 Fee Interest 540,000 55.0 (2.6 ) (1) Sales price represents the gross sales price for a property or the gross asset valuation for interests in a property. (2) Gain (loss) on sale amounts do not include adjustments for expenses recorded in subsequent periods.

Debt and Preferred Equity Inves

Debt and Preferred Equity Investments	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Debt and Preferred Equity Investments	Debt and Preferred Equity Investments Below is a summary of the activity relating to our debt and preferred equity investments for the nine months ended September 30, 2018 and the twelve months ended December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Balance at beginning of period (1) $ 2,114,041 $ 1,640,412 Debt investment originations/accretion (2) 664,961 1,142,591 Preferred equity investment originations/accretion (2) 6,305 144,456 Redemptions/sales/syndications/amortization (3) (808,250 ) (813,418 ) Balance at end of period (1) $ 1,977,057 $ 2,114,041 (1) Net of unamortized fees, discounts, and premiums. (2) Accretion includes amortization of fees and discounts and paid-in-kind investment income. (3) Certain participations in debt investments that were sold or syndicated did not meet the conditions for sale accounting are included in other assets and other liabilities on the consolidated balance sheets. Debt Investments As of September 30, 2018 and December 31, 2017 , we held the following debt investments with an aggregate weighted average current yield of 8.92% at September 30, 2018 (in thousands): Loan Type September 30, 2018 September 30, 2018 Senior September 30, 2018 (1) December 31, 2017 (1) Maturity Date (2) Fixed Rate Investments: Mezzanine Loan (3a) $ — $ 1,160,000 $ 210,832 $ 204,005 March 2020 Mezzanine Loan — 15,000 3,500 3,500 September 2021 Mezzanine Loan — 147,000 24,927 24,913 April 2022 Mezzanine Loan — 280,000 36,069 34,600 August 2022 Mezzanine Loan — 83,689 12,704 12,699 November 2023 Mezzanine Loan (3b) — 115,000 12,939 12,932 June 2024 Mezzanine Loan — 95,000 30,000 30,000 January 2025 Mezzanine Loan — 340,000 15,000 15,000 November 2026 Mezzanine Loan — 1,657,500 55,250 55,250 June 2027 Mortgage/Jr. Mortgage Loan (4) — — — 250,464 Mortgage Loan (5)(6) — — — 26,366 Loan Type September 30, 2018 September 30, 2018 Senior September 30, 2018 (1) December 31, 2017 (1) Maturity Date (2) Mortgage Loan (7) — — — 239 Total fixed rate $ — $ 3,893,189 $ 401,221 $ 669,968 Floating Rate Investments: Mezzanine Loan (8) — 20,523 10,977 10,934 August 2018 Mezzanine Loan (9) 2,325 45,025 35,168 34,879 October 2018 Mezzanine Loan (3c) — 150,000 15,368 15,381 December 2018 Mezzanine Loan (3d) — — 14,856 14,869 December 2018 Mezzanine Loan — 33,000 26,987 26,927 December 2018 Mezzanine Loan 3,607 30,438 10,403 8,550 January 2019 Mezzanine Loan (3e)(10) 795 — 15,150 15,148 March 2019 Mezzanine Loan — 38,000 21,977 21,939 March 2019 Mezzanine Loan (11) — 40,000 19,972 19,982 April 2019 Mezzanine Loan (11) — 37,891 18,380 34,947 April 2019 Mezzanine Loan — 175,000 37,404 37,250 April 2019 Mezzanine Loan — 265,000 24,928 24,830 April 2019 Mortgage/Jr. Mortgage Participation Loan 17,186 228,516 82,517 71,832 August 2019 Mortgage/Mezzanine Loan (12) — — 19,999 19,940 August 2019 Mezzanine Loan (13) — 65,000 14,998 14,955 August 2019 Mortgage/Mezzanine Loan 5,905 — 180,339 143,919 September 2019 Mezzanine Loan — 350,000 34,847 34,737 October 2019 Mortgage/Mezzanine Loan 387 — 39,338 — December 2019 Mortgage/Mezzanine Loan 13,048 — 56,624 43,845 January 2020 Mezzanine Loan 812 574,120 78,841 75,834 January 2020 Mortgage Loan 13,579 — 86,058 — February 2020 Mezzanine Loan 2,944 312,310 51,669 — March 2020 Mortgage/Mezzanine Loan 27,776 — 288,811 — April 2020 Mezzanine Loan 6,095 36,786 12,141 11,259 July 2020 Mezzanine Loan 41,309 355,148 85,955 75,428 November 2020 Mortgage and Mezzanine Loan 35,631 — 96,185 88,989 December 2020 Mortgage and Mezzanine Loan — — 35,236 35,152 December 2020 Jr. Mortgage Participation/Mezzanine Loan — 60,000 15,657 15,635 July 2021 Mortgage/Mezzanine Loan (14) — — — 162,553 Mortgage/Mezzanine Loan (14) — — — 74,755 Mortgage/Mezzanine Loan (15) — — — 23,609 Mezzanine Loan (16) — — — 12,174 Mezzanine Loan (17) — — — 37,851 Mezzanine Loan (17) — — — 14,855 Mortgage/Mezzanine Loan (6) — — — 16,969 Mezzanine Loan (7) — — — 59,723 Total floating rate $ 171,399 $ 2,816,757 $ 1,430,785 $ 1,299,650 Total $ 171,399 $ 6,709,946 $ 1,832,006 $ 1,969,618 (1) Carrying value is net of discounts, premiums, original issue discounts and deferred origination fees. (2) Represents contractual maturity, excluding any unexercised extension options. (3) Carrying value is net of the following amounts that were sold or syndicated, which are included in other assets and other liabilities on the consolidated balance sheets as a result of the transfers not meeting the conditions for sale accounting: (a) $1.3 million , (b) $12.0 million , (c) $14.6 million , (d) $14.1 million , and (e) $5.1 million . (4) These loans were conveyed to SL Green in the form of a distribution in March 2018. (5) In September 2014, we acquired a $26.4 million mortgage loan at a $0.2 million discount and a $5.7 million junior mortgage participation at a $5.7 million discount. The junior mortgage participation has been a nonperforming loan since acquisition, is currently on non-accrual status and has no carrying value. (6) This loan was repaid in August 2018. (7) This loan was repaid in September 2018. (8) This loan was conveyed to SL Green in the form of a distribution in October 2018. (9) This loan was extended in October 2018. (10) This loan was extended in March 2018. (11) This loan was extended in April 2018. (12) This loan was extended in August 2018. (13) This loan was extended in July 2018. (14) This loan was repaid in February 2018. (15) This loan was sold in May 2018. (16) This loan was conveyed to SL Green in the form of a distribution in July 2018. (17) This loan was repaid in July 2018. Preferred Equity Investments As of September 30, 2018 and December 31, 2017 , we held the following preferred equity investments with an aggregate weighted average current yield of 5.73% at September 30, 2018 (in thousands): Type September 30, 2018 September 30, 2018 Senior September 30, 2018 (1) December 31, 2017 (1) Maturity (2) Preferred Equity $ — $ 272,000 $ 145,051 $ 144,423 April 2021 Total $ — $ 272,000 $ 145,051 $ 144,423 (1) Carrying value is net of deferred origination fees. (2) Represents contractual maturity, excluding any unexercised extension options. At September 30, 2018 , all debt and preferred equity investments were performing in accordance with the terms of the relevant investments, with the exception of one mezzanine loan which was in maturity default. The mezzanine note receivable was conveyed in the form of a distribution to SL Green in October 2018. At December 31, 2017, all debt and preferred equity investments were performing in accordance with the terms of the relevant investments with the exception of a junior mortgage participation acquired in September 2014, which was acquired for zero and has a carrying value of zero , as discussed in subnote 5 of the Debt Investments table above, and our investment in 2 Herald Square, which was purchased in maturity default and was subsequently conveyed to SL Green in the form of a distribution in the first quarter of 2018. In May 2018, SL Green was the successful bidder for the leasehold interest at the foreclosure of the asset and assigned the Company a 49.0% tenancy in common interest in the leasehold interest. We have determined that we have one portfolio segment of financing receivables at September 30, 2018 and December 31, 2017 , comprising commercial real estate which is primarily recorded in debt and preferred equity investments. Included in other assets is an additional amount of financing receivables totaling $111.5 million and $93.4 million at September 30, 2018 and December 31, 2017 , respectively. No financing receivables were 90 days past due at September 30, 2018 .

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in Unconsolidated Joint Ventures	Investments in Unconsolidated Joint Ventures We have investments in several real estate joint ventures with various partners. As of September 30, 2018 and December 31, 2017 , none of our investments in unconsolidated joint ventures were VIEs. All of the investments below are voting interest entities. As we do not control the joint ventures listed below, we account for them under the equity method of accounting. The table below provides general information on each of our joint ventures as of September 30, 2018 : Property Partner Ownership Interest (1) Economic Interest (1) Unaudited Approximate Square Feet Acquisition Date (2) Acquisition Price (2) (in thousands) 919 Third Avenue (3) New York State Teacher's Retirement System 51.00% 51.00% 1,454,000 January 2007 $ 1,256,727 131-137 Spring Street Invesco Real Estate 20.00% 20.00% 68,342 August 2015 277,750 2 Herald Square (4) (4) 49.00% 49.00% 369,000 May 2018 266,000 (1) Ownership interest and economic interest represent the Company's interests in the joint venture as of September 30, 2018 . Changes in ownership or economic interests within the current year are disclosed in the notes below. (2) Acquisition date and price represent the date on which the Company initially acquired an interest in the joint venture and the actual or implied gross purchase price for the joint venture on that date. Acquisition date and price are not adjusted for subsequent acquisitions or dispositions of interest. (3) In January 2018, the partnership agreement for our investment was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $54.9 million fair value adjustment in the consolidated statement of operations. This fair value was allocated to the assets and liabilities, including identified intangibles of the property. (4) In May 2018, SL Green assigned the Company a 49.0% tenancy-in-common interest in the leasehold interest in 2 Herald Square and entered into an agreement to sell this investment. Consolidation of this investment is not required as such interest does not qualify as a VIE and does not meet the control requirement for consolidation. Accordingly, we account for this investment using the equity method of accounting. We use the equity method of accounting because the shared decision-making involved in a tenancy-in-common interest investment provides us with significant influence on the operating and financial decisions of this investment. Acquisition, Development and Construction Arrangements Based on the characteristics of the following arrangements, which are similar to those of an investment, combined with the expected residual profit of not greater than 50% , we have accounted for these debt and preferred equity investments under the equity method. As of September 30, 2018 and December 31, 2017 , the carrying value for acquisition, development and construction arrangements were as follows (in thousands): Loan Type September 30, 2018 December 31, 2017 Maturity Date Mezzanine Loan (1) $ — $ 26,716 Mezzanine Loan and Preferred Equity (2) — 100,000 $ — $ 126,716 (1) The Company was redeemed on this investment in July 2018. (2) The mezzanine loan was repaid and the preferred equity interest was redeemed in March 2018. Disposition of Joint Venture Interests or Properties The following table summarizes the investments in unconsolidated joint ventures disposed of during the nine months ended September 30, 2018 : Property Ownership Interest Disposition Date Type of Sale Gross Asset Valuation (in thousands) (1) Gain (Loss) on Sale (in thousands) (2) Mezzanine Loan (3) 33.33% August 2018 Repayment $ 15,000 N/A (1) Represents implied gross valuation for the joint venture or sales price of the property. (2) Represents the Company's share of the gain (loss). (3) Our investment in a joint venture that owned a mezzanine loan secured by a commercial property in midtown Manhattan was repaid after the joint venture received repayment of the underlying loan. Joint Venture Mortgages and Other Loans Payable We generally finance our joint ventures with non-recourse debt. In certain cases we have provided guarantees or master leases for tenant space, which terminate upon the satisfaction of specified circumstances or repayment of the underlying loans. The first mortgage notes and other loans payable collateralized by the respective joint venture properties and assignment of leases at September 30, 2018 and December 31, 2017 , respectively, are as follows (amounts in thousands): Property Economic Interest (1) Maturity Date Interest Rate (2) September 30, 2018 December 31, 2017 Fixed Rate Debt: 919 Third Avenue 51.00 % June 2023 5.12 % $ 500,000 $ — Floating Rate Debt: 131-137 Spring Street 20.00 % August 2020 L+ 1.55 % $ 141,000 $ 141,000 Total joint venture mortgages and other loans payable $ 641,000 $ 141,000 Deferred financing costs, net (2,031 ) (2,862 ) Total joint venture mortgages and other loans payable, net $ 638,969 $ 138,138 (1) Economic interest represents the Company's interests in the joint venture as of September 30, 2018 . Changes in ownership or economic interests, if any, within the current year are disclosed in the notes to the investment in unconsolidated joint ventures table above. (2) Interest rates as of September 30, 2018 . Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified. The combined balance sheets for the unconsolidated joint ventures at September 30, 2018 and December 31, 2017 are as follows (in thousands): September 30, 2018 December 31, 2017 Assets (1) Commercial real estate property, net $ 1,860,269 $ 273,116 Debt and preferred equity investments, net — 141,716 Other assets 773,530 15,735 Total assets $ 2,633,799 $ 430,567 Liabilities and members' equity (1) Mortgages and other loans payable, net $ 638,969 $ 138,138 Other liabilities 895,127 18,908 Members' equity 1,099,703 273,521 Total liabilities and members' equity $ 2,633,799 $ 430,567 Company's investments in unconsolidated joint ventures $ 477,686 $ 130,217 (1) The combined assets, liabilities and equity for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018. The combined statements of operations for the unconsolidated joint ventures for the three and nine months ended September 30, 2018 and 2017 are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Total revenues $ 42,037 $ 7,340 $ 112,399 $ 26,934 Operating expenses 6,659 182 18,925 636 Real estate taxes 9,178 381 22,674 1,013 Ground rent 3,106 — 3,106 — Interest expense, net of interest income 10,377 1,025 24,174 2,759 Amortization of deferred financing costs 277 283 831 837 Depreciation and amortization 12,607 2,102 37,701 6,304 Total expenses $ 42,204 $ 3,973 $ 107,411 $ 11,549 Net (loss) income (1) $ (167 ) $ 3,367 $ 4,988 $ 15,385 Company's equity in net income from unconsolidated joint ventures (1) $ (164 ) $ 2,927 $ 3,835 $ 10,362 (1) The combined statements of operation and the Company's equity in net income for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.

Mortgages and Other Loans Payab

Mortgages and Other Loans Payable	9 Months Ended
	Sep. 30, 2018
Mortgage Note and Other Loans Payable
Mortgages and Other Loans Payable	Mortgages and Other Loans Payable The first mortgages and other loans payable collateralized by the respective properties and assignment of leases or debt investments at September 30, 2018 and December 31, 2017 , respectively, were as follows (amounts in thousands): Property Maturity Date Interest Rate (1) September 30, 2018 December 31, 2017 Fixed Rate Debt: 315 West 33rd Street February 2027 4.24 % $ 250,000 $ 250,000 919 Third Avenue (2) — 500,000 Floating Rate Debt: 2017 Master Repurchase Agreement June 2019 L+ 2.34 % $ 300,000 $ 90,809 115 Spring Street September 2023 L+ 3.40 % 65,550 — Total mortgages and other loans payable $ 615,550 $ 840,809 Deferred financing costs, net of amortization (8,489 ) (11,161 ) Total mortgages and other loans payable, net $ 607,061 $ 829,648 (1) Interest rate as of September 30, 2018 . Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified. (2) Our investment in the property was deconsolidated as of January 1, 2018. See Note 6, "Investments in Unconsolidated Joint Ventures". At September 30, 2018 and December 31, 2017 , the gross book value of the properties and debt and preferred equity investments collateralizing the mortgages and other loans payable, not including assets held for sale, was approximately $1.0 billion and $1.9 billion , respectively. Master Repurchase Agreements The Company has entered into two Master Repurchase Agreements, or MRAs, known as the 2016 MRA and 2017 MRA, which provide us with the ability to sell certain debt investments with a simultaneous agreement to repurchase the same at a certain date or on demand. We seek to mitigate risks associated with our repurchase agreement by managing the credit quality of our assets, early repayments, interest rate volatility, liquidity, and market value. The margin call provisions under our repurchase facilities permit valuation adjustments based on capital markets activity, and are not limited to collateral-specific credit marks. To monitor credit risk associated with our debt investments, our asset management team regularly reviews our investment portfolio and is in contact with our borrowers in order to monitor the collateral and enforce our rights as necessary. The risk associated with potential margin calls is further mitigated by our ability to recollateralize the facility with additional assets from our portfolio of debt investments and our ability to satisfy margin calls with cash or cash equivalents. In June 2017, we entered into the 2017 MRA, with a maximum facility capacity of $300.0 million . In April 2018, we increased the maximum facility capacity to $400.0 million . The facility bears interest on a floating rate basis at a spread to 30-day LIBOR based on the pledged collateral and advance rate and has an initial one year term, with two one year extension options. In June 2018, we exercised a one year extension option. At September 30, 2018 , the facility had an outstanding balance of $299.4 million , net of deferred financing costs. In July 2016, we entered into the 2016 MRA, with a maximum facility capacity of $300.0 million . In June 2018, we terminated the 2016 MRA. The facility bore interest ranging from 225 and 400 basis points over 30-day LIBOR depending on the pledged collateral and had an initial two -year term, with a one year extension option. Since December 6, 2015, we had been required to pay monthly in arrears a 25 basis point fee on the excess of $150.0 million over the average daily balance during the period when the average daily balance was less than $150.0 million .

Corporate Indebtedness

Corporate Indebtedness	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Corporate Indebtedness	Corporate Indebtedness 2017 Credit Facility In November 2017, the Company, SL Green and the Operating Partnership entered into an amendment to the credit facility, referred to as the 2017 credit facility, that was originally entered into in November 2012, or the 2012 credit facility. The amendment resulted in the Company no longer being a borrower and instead is providing a guarantee of the facility. The 2012 credit facility had a carrying value of $1.2 billion , net of deferred financing costs, as of the amendment date and was removed from our consolidated balance sheet and shown as a non-cash capital contribution. SL Green and the Operating Partnership remain borrowers, jointly and severally obligated, under the 2017 credit facility. As of September 30, 2018 , the 2017 credit facility consisted of a $1.5 billion revolving credit facility, a $1.3 billion term loan (or "Term Loan A"), and a $200.0 million term loan (or "Term Loan B") with maturity dates of March 31, 2022, March 31, 2023, and November 21, 2024, respectively. The revolving credit facility has two six -month as-of-right extension options to March 31, 2023. SL Green and the Operating Partnership also have an option, subject to customary conditions, to increase the capacity of the credit facility to $4.5 billion at any time prior to the maturity dates for the revolving credit facility and term loans without the consent of existing lenders, by obtaining additional commitments from the existing lenders and other financial institutions. As of September 30, 2018 , SL Green and the Operating Partnership had $11.8 million of outstanding letters of credit, $145.0 million drawn under the revolving credit facility and $1.5 billion outstanding under the term loan facilities, with total undrawn capacity of $1.3 billion under the 2017 credit facility. At September 30, 2018 and December 31, 2017 , the revolving credit facility had a carrying value of $136.7 million and $30.3 million , respectively, net of deferred financing costs. At September 30, 2018 and December 31, 2017 , the term loan facilities had a carrying value of $1.5 billion and $1.5 billion , respectively, net of deferred financing costs. The 2017 credit facility includes certain restrictions and covenants (see Restrictive Covenants below). Senior Unsecured Notes The following table sets forth our senior unsecured notes and other related disclosures as of September 30, 2018 and December 31, 2017 , respectively, by scheduled maturity date (amounts in thousands): Issuance September 30, September 30, December 31, Coupon (1) Initial Maturity Date March 16, 2010 (2) $ 250,000 $ 250,000 $ 250,000 7.75 % 10 March 2020 November 15, 2012 (3) 300,000 304,421 305,163 4.50 % 10 December 2022 December 17, 2015 (2) 100,000 100,000 100,000 4.27 % 10 December 2025 August 5, 2011 (2) (4) — — 249,953 $ 650,000 $ 654,421 $ 905,116 Deferred financing costs, net (3,081 ) (4,049 ) $ 650,000 $ 651,340 $ 901,067 (1) Interest on the senior unsecured notes is payable semi-annually with principal and unpaid interest due on the scheduled maturity dates. (2) Issued by SL Green, the Operating Partnership and ROP, as co-obligors. (3) In October 2017, SL Green, the Operating Partnership, and ROP, as co-obligors, issued an additional $100.0 million of 4.50% senior unsecured notes due December 2022. The notes were priced at 105.334% . (4) Balance was repaid in August 2018. We provide a guaranty of the Operating Partnership's obligations under its 3.25% Senior Notes due 2022, which were issued in October 2017 and will mature in October 2022. As of September 30, 2018 , the 3.25% Senior Notes due 2022 had a carrying value of $499.6 million . We also provide a guaranty of the Operating Partnership's obligations under its $350.0 million Senior Notes due 2021, which were issued in August 2018. The notes bear interest at a floating rate, reset quarterly, equal to three-month LIBOR plus 98 basis points. The notes will mature in August 2021 and can be redeemed at par beginning in August 2019. Restrictive Covenants The terms of the 2017 credit facility and certain of our senior unsecured notes include certain restrictions and covenants which may limit, among other things, SL Green's ability to pay dividends, make certain types of investments, incur additional indebtedness, incur liens and enter into negative pledge agreements and dispose of assets, and which require compliance with financial ratios relating to the maximum ratio of total indebtedness to total asset value, a minimum ratio of EBITDA to fixed charges, a maximum ratio of secured indebtedness to total asset value and a maximum ratio of unsecured indebtedness to unencumbered asset value. The dividend restriction referred to above provides that SL Green will not during any time when a default is continuing, make distributions with respect to SL Green's common stock or other equity interests, except to enable SL Green to continue to qualify as a REIT for Federal income tax purposes. As of September 30, 2018 and December 31, 2017 , we were in compliance with all such covenants. Principal Maturities Combined aggregate principal maturities of mortgages and other loans payable, and senior unsecured notes as of September 30, 2018 , including as-of-right extension options and put options, were as follows (in thousands): Scheduled Principal Senior Unsecured Notes Total Remaining 2018 $ — $ — $ — $ — 2019 — — — — 2020 — 300,000 250,000 550,000 2021 — — — — 2022 — — 300,000 300,000 Thereafter — 315,550 100,000 415,550 $ — $ 615,550 $ 650,000 $ 1,265,550 Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest expense before capitalized interest $ 17,052 $ 34,658 $ 51,729 $ 96,740 Interest capitalized (1,594 ) (31 ) (3,908 ) (533 ) Interest income — — (3 ) (5 ) Interest expense, net $ 15,458 $ 34,627 $ 47,818 $ 96,202

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Cleaning/ Security/ Messenger and Restoration Services Alliance Building Services, or Alliance, and its affiliates are partially owned by Gary Green, a son of Stephen L. Green, the chairman of SL Green's board of directors, and provide services to certain properties owned by us. Alliance’s affiliates include First Quality Maintenance, L.P., or First Quality, Classic Security LLC, Bright Star Couriers LLC and Onyx Restoration Works, and provide cleaning, extermination, security, messenger, and restoration services, respectively. In addition, First Quality has the non-exclusive opportunity to provide cleaning and related services to individual tenants at our properties on a basis separately negotiated with any tenant seeking such additional services. The Service Corporation has entered into an arrangement with Alliance whereby it will receive a profit participation above a certain threshold for services provided by Alliance to certain tenants at certain buildings above the base services specified in their lease agreements. Income earned from the profit participation, which is included in other income on the consolidated statements of operations, was $0.9 million and $2.6 million for the three and nine months ended September 30, 2018 , respectively, and was $0.8 million and $2.5 million for the three and nine months ended September 30, 2017 , respectively. We also recorded expenses, inclusive of capitalized expenses, of $2.4 million and $7.0 million for the three and nine months ended September 30, 2018 , respectively, for these services (excluding services provided directly to tenants), and $2.6 million and $7.1 million for the three and nine months ended September 30, 2017 , respectively. Allocated Expenses from SL Green Property operating expenses include an allocation of salary and other operating costs from SL Green based on square footage of the related properties. Such amount was approximately $2.6 million and $8.2 million for the three and nine months ended September 30, 2018 , respectively. The amount was $3.0 million and $9.2 million for the three and nine months ended September 30, 2017 , respectively. Insurance We obtain insurance coverage through an insurance program administered by SL Green. In connection with this program, we incurred insurance expense of approximately $1.0 million and $3.2 million for the three and nine months ended September 30, 2018 , respectively. We incurred insurance expense of approximately $1.3 million and $4.1 million for the three and nine months ended September 30, 2017 , respectively. Related Party Payable to SL Green On August 22, 2016, we issued a promissory note to our parent company in the amount of $23.8 million which bears interest at an annual rate of 6.0% , compounded quarterly. This note matured on August 22, 2018.

Preferred Units

Preferred Units	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Preferred Units	Preferred Units Through a consolidated subsidiary, we have authorized up to 109,161 3.50% Series A Preferred Units of limited partnership interest, or the Subsidiary Series A Preferred Units, with a liquidation preference of $1,000.00 per unit. In August 2015, the Company issued 109,161 Subsidiary Series A Preferred Units in conjunction with an acquisition. The Subsidiary Series A Preferred unitholders receive annual dividends of $35.00 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Subsidiary Series A Preferred Units can be redeemed at any time, at the option of the unitholder, either for cash or are convertible on a one-for-one basis, into the Series B Preferred Units of limited partnership interest, or the Subsidiary Series B Preferred Units. The Subsidiary Series B Preferred Units can be converted at any time, at the option of the unitholder, into a number of common stock equal to 6.71348 shares of SL Green common stock for each Subsidiary Series B Preferred Unit. As of September 30, 2018 , no Subsidiary Series B Preferred Units have been issued. ASC 815 Derivatives and Hedging requires bifurcation of certain embedded derivative instruments, such as conversion features in convertible equity instruments, and their measurement at fair value for accounting purposes. The conversion feature embedded in the Subsidiary Series A Preferred Units was evaluated, and it was determined that the conversion feature should be bifurcated from its host instrument and accounted for as a freestanding derivative. The derivative is reported as a derivative liability in accrued interest and other liabilities on the accompanying consolidated balance sheet and is adjusted to its fair value at each reporting date, with a corresponding adjustment to interest expense, net of interest income. The embedded derivative for the Subsidiary Series A Preferred Units was initially recorded at a fair value of zero on July 22, 2015, the date of issuance. At September 30, 2018 , the carrying amount of the derivative remained at zero .

Partners' Capital

Partners' Capital	9 Months Ended
	Sep. 30, 2018
Partners' Capital Notes [Abstract]
Partners' Capital	Partners' Capital Since consummation of the Merger on January 25, 2007, the Operating Partnership has owned all the economic interests in us either by direct ownership or by indirect ownership through our general partner, which is its wholly-owned subsidiary. Intercompany transactions between SL Green and us are generally recorded as contributions and distributions.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We are required to disclose fair value information with regard to our financial instruments, whether or not recognized in the consolidated balance sheets, for which it is practical to estimate fair value. The FASB guidance defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. We measure and/or disclose the estimated fair value of financial assets and liabilities based on a hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity and the reporting entity’s own assumptions about market participant assumptions. This hierarchy consists of three broad levels: Level 1 - quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date; Level 2 - inputs other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly; and Level 3 - unobservable inputs for the asset or liability that are used when little or no market data is available. We follow this hierarchy for our assets and liabilities measured at fair value on a recurring and nonrecurring basis. In instances in which the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level of input that is significant to the fair value measurement in its entirety. Our assessment of the significance of the particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. We determine other than temporary impairment in real estate investments and debt and preferred equity investments, including intangibles primarily utilizing cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs. In January 2018, the partnership agreement for our investment in 919 Third Avenue was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $54.9 million fair value adjustment in the consolidated statement of operations. This fair value was determined using a third party valuation which primarily utilized cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs. The fair value of derivative instruments is based on current market data received from financial sources that trade such instruments and are based on prevailing market data and derived from third party proprietary models based on well-recognized financial principles and reasonable estimates about relevant future market conditions, which are classified as Level 2 inputs. The financial assets and liabilities that are not measured at fair value on our consolidated balance sheets include cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses, debt and preferred equity investments, mortgages and other loans payable and other secured and unsecured debt. The carrying amount of cash and cash equivalents, restricted cash, accounts receivable, and accounts payable and accrued expenses reported in our consolidated balance sheets approximates fair value due to the short term nature of these instruments. The fair value of debt and preferred equity investments, which is classified as Level 3, is estimated by discounting the future cash flows using current interest rates at which similar loans with the same maturities would be made to borrowers with similar credit ratings. The fair value of borrowings, which is classified as Level 3, is estimated by discounting the contractual cash flows of each debt instrument to their present value using adjusted market interest rates, which is provided by a third-party specialist. The following table provides the carrying value and fair value of these financial instruments as of September 30, 2018 and December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Carrying Value (1) Fair Value Carrying Value (1) Fair Value Debt and preferred equity investments $ 1,977,057 (2) $ 2,114,041 (2) Fixed rate debt $ 904,421 $ 907,337 $ 1,655,116 $ 1,715,501 Variable rate debt 365,550 382,438 90,809 92,087 $ 1,269,971 $ 1,289,775 $ 1,745,925 $ 1,807,588 (1) Amounts exclude net deferred financing costs. (2) At September 30, 2018 , debt and preferred equity investments had an estimated fair value ranging between $2.0 billion and $2.2 billion . At December 31, 2017 , debt and preferred equity investments had an estimated fair value ranging between $2.1 billion and $2.3 billion . Disclosure about fair value of financial instruments was based on pertinent information available to us as of September 30, 2018 and December 31, 2017 . Although we are not aware of any factors that would significantly affect the reasonable fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since that date and current estimates of fair value may differ significantly from the amounts presented herein.

Financial Instruments_ Derivati

Financial Instruments: Derivatives and Hedging	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments: Derivatives and Hedging	Financial Instruments: Derivatives and Hedging In the normal course of business, we use a variety of commonly used derivative instruments, such as interest rate swaps, caps, collar and floors, to manage, or hedge interest rate risk. We hedge our exposure to variability in future cash flows for forecasted transactions in addition to anticipated future interest payments on existing debt. We recognize all derivatives on the balance sheet at fair value. Derivatives that are not hedges are adjusted to fair value through earnings. If a derivative is a hedge, depending on the nature of the hedge, changes in the fair value of the derivative will either be offset against the change in fair value of the hedge asset, liability, or firm commitment through earnings, or recognized in other comprehensive income until the hedged item is recognized in earnings. The ineffective portion of a derivative's change in fair value will be immediately recognized in earnings. Reported net income and equity may increase or decrease prospectively, depending on future levels of interest rates and other variables affecting the fair values of derivative instruments and hedged items, but will have no effect on cash flows. Currently, all of our designated derivative instruments are effective hedging instruments. As of September 30, 2018 , the Company had not designated any interest rate swap agreements on any debt investment. Gains and losses on terminated hedges are included in accumulated other comprehensive income, and are recognized into earnings over the term of the related senior unsecured notes. As of September 30, 2018 and December 31, 2017 , the deferred net losses from these terminated hedges, which are included in accumulated other comprehensive income relating to net unrealized loss on derivative instruments, was approximately zero and $1.3 million , respectively. The following table presents the effect of our derivative financial instruments that are designated and qualify as hedging instruments on the consolidated statements of operations for the three months ended September 30, 2018 and 2017 , respectively (in thousands): Amount of Loss Recognized in Other Comprehensive Loss (Effective Portion) Location of Loss Reclassified from Accumulated Other Comprehensive Loss into Income Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Location of Gain Recognized in Income on Derivative Amount of Gain Recognized into Income (Ineffective Portion) Three Months Ended September 30, Three Months Ended September 30, Three Months Ended September 30, Derivative 2018 2017 2018 2017 2018 2017 Interest Rate Swap $ — $ — Interest expense $ — $ 89 Interest expense $ — $ — The following table presents the effect of our derivative financial instruments that are designated and qualify as hedging instruments on the consolidated statements of operations for the nine months ended September 30, 2018 and 2017 , respectively (in thousands): Amount of Loss Recognized in Other Comprehensive Loss (Effective Portion) Location of Loss Reclassified from Accumulated Other Comprehensive Loss into Income Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Location of Gain Recognized in Income on Derivative Amount of Gain Recognized into Income (Ineffective Portion) Nine Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, Derivative 2018 2017 2018 2017 2018 2017 Interest Rate Swap $ — $ — Interest expense $ — $ 269 Interest expense $ — $ —

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings As of September 30, 2018 , we were not involved in any material litigation nor, to management's knowledge, was any material litigation threatened against us or our portfolio which if adversely determined could have a material adverse impact on us. Guarantees During the nine months ended September 30, 2018 , Ticonderoga Insurance Company, or Ticonderoga, a Vermont licensed captive insurance company and an affiliate of SL Green, became a member of the Federal Home Loan Bank of New York, or FHLBNY. As a member, Ticonderoga may borrow funds from the FHLBNY in the form of secured advances. As of September 30, 2018 , certain debt and preferred equity investments of the Company were pledged as collateral to secure advances under the FHLBNY facility. If Ticonderoga or SL Green are unable to repay the advances upon the termination of Ticonderoga's membership, the maximum potential amount of future payments the Company could be required to make under the secured advances is $13.0 million . Environmental Matters Our management believes that the properties are in compliance in all material respects with applicable Federal, state and local ordinances and regulations regarding environmental issues. Management is not aware of any environmental liability that it believes would have a materially adverse impact on our financial position, results of operations or cash flows. Management is unaware of any instances in which it would incur significant environmental cost if any of our properties were sold. Capital and Ground Leases Arrangements The following is a schedule of future minimum lease payments under non-cancellable operating leases with initial terms in excess of one year as of September 30, 2018 (in thousands): Non-cancellable operating leases Remaining 2018 $ 4,934 2019 19,736 2020 19,736 2021 19,886 2022 17,730 2023 15,424 Thereafter 237,011 Total minimum lease payments $ 334,457

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The Company has two reportable segments, real estate and debt and preferred equity investments. We evaluate real estate performance and allocate resources based on earnings contribution to income from continuing operations. The primary sources of revenue are generated from tenant rents and escalations and reimbursement revenue. Real estate property operating expenses consist primarily of security, maintenance, utility costs, insurance, real estate taxes and ground rent expense (at certain applicable properties). See Note 5, "Debt and Preferred Equity Investments," for additional details on our debt and preferred equity investments. Selected consolidated results of operations for the three and nine months ended September 30, 2018 and 2017 , and selected asset information as of September 30, 2018 and December 31, 2017 , regarding our operating segments are as follows (in thousands): Real Estate Segment Debt and Preferred Equity Segment Total Company Total revenues: Three months ended: September 30, 2018 $ 149,462 $ 49,125 $ 198,587 September 30, 2017 193,962 47,946 241,908 Nine months ended: September 30, 2018 $ 472,777 $ 143,087 $ 615,864 September 30, 2017 577,151 148,924 726,075 Net income Three months ended: September 30, 2018 $ 39,354 $ 34,154 $ 73,508 September 30, 2017 24,722 39,988 64,710 Nine months ended: September 30, 2018 $ 172,068 $ 100,866 $ 272,934 September 30, 2017 7,342 131,507 138,849 Total assets As of: September 30, 2018 $ 5,204,346 $ 2,100,202 $ 7,304,548 December 31, 2017 6,182,431 2,359,077 8,541,508 Interest costs for the debt and preferred equity segment includes actual costs incurred for investments collateralizing the MRAs. Interest is imputed on the remaining investments using our corporate borrowing cost. We also allocate loan loss reserves, net of recoveries, and transaction related costs to the debt and preferred equity segment. We do not allocate marketing, general and administrative expenses to the debt and preferred equity segment since the use of personnel and resources is dependent on transaction volume between the two segments and varies period over period. In addition, we base performance on the individual segments excluding marketing, general and administrative expenses. All other expenses, except interest, relate entirely to the real estate assets. For the three and nine months ended September 30, 2018 marketing, general and administrative expenses totaled $0.1 million and $0.4 million , respectively. For the three and nine months ended September 30, 2017 marketing, general and administrative expenses totaled $0.1 million and $0.3 million , respectively. There were no transactions between the above two segments.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include our accounts and those of our subsidiaries, which are wholly-owned or controlled by us. Entities which we do not control through our voting interest and entities which are variable interest entities, but where we are not the primary beneficiary, are accounted for under the equity method. See Note 5, "Debt and Preferred Equity Investments" and Note 6, "Investments in Unconsolidated Joint Ventures." All significant intercompany balances and transactions have been eliminated. We consolidate a VIE in which we are considered the primary beneficiary. The primary beneficiary is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE.
Investment in Commercial Real Estate Properties	Investment in Commercial Real Estate Properties We allocate the purchase price of real estate to land and building (inclusive of tenant improvements) and, if determined to be material, intangibles, such as the value of above- and below-market leases and origination costs associated with the in-place leases. We depreciate the amount allocated to building (inclusive of tenant improvements) over their estimated useful lives, which generally range from three to 40 years . We amortize the amount allocated to the above- and below-market leases over the remaining term of the associated lease, which generally range from one to 14 years , and record it as either an increase (in the case of below-market leases) or a decrease (in the case of above-market leases) to rental income. We amortize the amount allocated to the values associated with in-place leases over the expected term of the associated lease, which generally ranges from one to 14 years . If a tenant vacates its space prior to the contractual termination of the lease and no rental payments are being made on the lease, any unamortized balance of the related intangible will be written off. The tenant improvements and origination costs are amortized as an expense over the remaining life of the lease (or charged against earnings if the lease is terminated prior to its contractual expiration date). We assess fair value of the leases based on estimated cash flow projections that utilize appropriate discount and capitalization rates and available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known trends, and market/economic conditions that may affect the property. To the extent acquired leases contain fixed rate renewal options that are below-market and determined to be material, we amortize such below-market lease value into rental income over the renewal period. On a periodic basis, we assess whether there are any indications that the value of our real estate properties may be other than temporarily impaired or that their carrying value may not be recoverable. A property's value is considered impaired if management's estimate of the aggregate future cash flows (undiscounted) to be generated by the property is less than the carrying value of the property. To the extent impairment has occurred, the loss will be measured as the excess of the carrying amount of the property over the calculated fair value of the property. We also evaluate our real estate properties for impairment when a property has been classified as held for sale. Real estate assets held for sale are valued at the lower of their carrying value or fair value less costs to sell.
Investments in Unconsolidated Joint Ventures	Investments in Unconsolidated Joint Ventures We assess our investments in unconsolidated joint ventures for recoverability, and if it is determined that a loss in value of the investment is other than temporary, we write down the investment to its fair value. We evaluate our equity investments for impairment based on the joint ventures' projected discounted cash flows.
Reserve for Possible Credit Losses	Reserve for Possible Credit Losses The reserve for possible credit losses in connection with debt and preferred equity investments is the charge to earnings to increase the allowance for possible credit losses to the level that we estimate to be adequate, based on Level 3 data, considering delinquencies, loss experience and collateral quality. Other factors considered include geographic trends, product diversification, the size of the portfolio and current economic conditions. Based upon these factors, we establish a provision for possible credit loss on each individual investment. When it is probable that we will be unable to collect all amounts contractually due, the investment is considered impaired. Where impairment is indicated on an investment that is held to maturity, a valuation allowance is measured based upon the excess of the recorded investment amount over the fair value of the collateral. Any deficiency between the carrying amount of an asset and the calculated value of the collateral is charged to expense. We continue to assess or adjust our estimates based on circumstances of a loan and the underlying collateral. If additional information reflects increased recovery of our investment, we will adjust our reserves accordingly. There were no loan reserves recorded during the three and nine months ended September 30, 2018 and 2017 . Debt and preferred equity investments held for sale are carried at the lower of cost or fair market value using available market information obtained through consultation with dealers or other originators of such investments as well as discounted cash flow models based on Level 3 data pursuant to ASC 820-10. As circumstances change, management may conclude not to sell an investment designated as held for sale. In such situations, the investment will be reclassified at its net carrying value to debt and preferred equity investments held to maturity. For these reclassified investments, the difference between the current carrying value and the expected cash to be collected at maturity will be accreted into income over the remaining term of the investment.
Income Taxes	Income Taxes ROP is a disregarded entity of SL Green Operating Partnership, L.P. for federal income tax purposes, and, as a result, all income and losses of ROP are considered income and losses of SL Green Operating Partnership, L. P. No provision has been made for income taxes in the consolidated financial statements since such taxes, if any, are the responsibility of the individual partners of SL Green Operating Partnership, L.P.
Shares Contributed by Parent Company	Shares Contributed by Parent Company We present shares of SL Green common stock as a contra-equity account within general partner capital in our consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash investments, debt and preferred equity investments and accounts receivable. We place our cash investments with high quality financial institutions. The collateral securing our debt and preferred equity investments is located in the New York metropolitan area. See Note 5, "Debt and Preferred Equity Investments."
Reclassification	Reclassification Certain prior year balances have been reclassified to conform to our current year presentation.
Accounting Standards Updates	Accounting Standards Updates In August 2018, The Securities and Exchange Commission adopted a final rule that eliminated or amended disclosure requirements that were redundant or outdated in light of changes in its requirements, generally accepted accounting principles, or changes in the business environment. The commission also referred certain disclosure requirements to the Financial Accounting Standards Board for potential incorporation into generally accepted accounting principles. The Company assessed the impact of this rule and determined that the changes resulted in clarification or expansion of existing requirements. The Company adopted the rule on November 5, 2018 and it did not have a material impact on the Company’s consolidated financial statements. In August 2018, the FASB issued Accounting Standard Update (ASU) No. 2018-15, Intangibles - Goodwill and Other- Internal-Use Software (Topic 350-40), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. The amendments provide guidance on accounting for fees paid when the arrangement includes a software license and align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing costs to develop or obtain internal-use software. The guidance will be effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted. The Company has not yet adopted this new guidance and does not expect it to have a material impact on the Company’s consolidated financial statements when the new standard is implemented. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This amendment removed, modified and added the disclosure requirements under Topic 820. The changes are effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted for the removed or modified disclosures with adoption of the additional disclosures upon the effective date. The Company has not yet adopted this new guidance and does not expect it to have a material impact on the Company’s consolidated financial statements when the new standard is implemented. In February 2018, the FASB issued ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments- Overall (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. These amendments provide additional guidance related to equity securities without a readily determinable fair value, forward contracts and options purchased on those equity securities and fair value option liabilities. The Company adopted the guidance on July 1, 2018, and it did not have a material impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities, and in July 2018, the FASB issued ASU No. 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The amendments in the new standards will permit more flexibility in hedging interest rate risk for both variable rate and fixed rate financial instruments. The standards will also enhance the presentation of hedge results in the financial statements. The guidance is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company has not yet adopted the guidance, and does not expect a material impact on the Company’s consolidated financial statements when the new standards are implemented. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The guidance requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash. As a result, entities will no longer present transfers between these items on the statement of cash flows. The Company adopted the guidance on January 1, 2018 and has included the changes in restricted cash when reconciling the beginning-of-period and end-of-period total amounts on the statement of cash flows. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The guidance changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current ‘incurred loss’ model with an ‘expected loss’ approach. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 15, 2018. The Company has not yet adopted this new guidance and is currently evaluating the impact of adopting this new accounting standard on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases, and in July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements. This guidance requires lessees to recognize lease assets and lease liabilities for those leases classified as operating leases under the previous standard. Depending on the lease classification, lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The accounting applied by a lessor, inclusive of the effect of a practical expedient offered in ASU No. 2018-11 that allows lessors to not separate non-lease components from the related lease components under certain conditions, which the Company expects most of its leases to qualify for and to adopt, is largely unchanged from that applied under the previous standard. However, the Company will apply this guidance to the ground leases under which the Company is lessee. The Company is required to record a liability for the obligation to make payments under the lease and an asset for the right to use the underlying asset during the lease term and will also apply the new expense recognition requirements given the lease classification. While the Company is continuing to assess all potential impacts of the standard, we expect total liabilities and total assets to increase by $0.1 to $0.2 billion as of the date of adoption. This guidance is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The Company expects to adopt this guidance January 1, 2019 and will apply the modified retrospective approach, and anticipates electing the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classification for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. In January 2016, the FASB issued ASU 2016-01 (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. The guidance requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value through earnings, to record changes in instrument-specific credit risk for financial liabilities measured under the fair value option in other comprehensive income, use the exit price notion when measuring an instrument’s fair value for disclosure and to separately present financial assets and liabilities by measurement category and form of instrument on the balance sheet or in the notes to the financial statements. The Company adopted the guidance effective January 1, 2018, and it had no impact on the Company’s consolidated financial statements. In May 2014, the FASB issued a new comprehensive revenue recognition guidance which requires us to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods and services (ASU 2014-09). The FASB also issued implementation guidance in March 2016, April 2016 and May 2016 - ASU’s 2016-08, 2016-10 and 2016-12, respectively. The Company adopted this guidance on January 1, 2018. Since the Company’s revenue is related to leasing activities, the adoption of this guidance did not have a material impact on the consolidated financial statements. The new guidance is applicable to service contracts with joint ventures for which the Company earns property management fees, leasing commissions and development and construction fees. The adoption of this new guidance did not change the accounting for these fees as the pattern of recognition of revenue does not change with the new guidance. We will continue to recognize revenue over time on these contracts because the customer simultaneously receives and consumes the benefits provided by our performance. In February 2017, the FASB issued ASU No. 2017-05 to clarify the scope of asset derecognition guidance in Subtopic 610-20, which also provided guidance on accounting for partial sales of nonfinancial assets. Subtopic 610-20 was issued in May 2014 as part of ASU 2014-09. The Company adopted this guidance on January 1, 2018, and applied the modified retrospective approach. The Company elected to adopt the practical expedient under ASC 606, Revenue from Contracts with Customers, which allows an entity to apply the guidance only to contracts with non-customers that are open based on ASU 360-20, Real Estate Sales, (i.e. failed sales) as of the adoption date. The adoption had no impact on the consolidated financial statements as the Company had no open contracts based on ASC 360-20 as of December 31, 2017 .
Fair Value Measurements	Fair Value Measurements We are required to disclose fair value information with regard to our financial instruments, whether or not recognized in the consolidated balance sheets, for which it is practical to estimate fair value. The FASB guidance defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. We measure and/or disclose the estimated fair value of financial assets and liabilities based on a hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity and the reporting entity’s own assumptions about market participant assumptions. This hierarchy consists of three broad levels: Level 1 - quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date; Level 2 - inputs other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly; and Level 3 - unobservable inputs for the asset or liability that are used when little or no market data is available. We follow this hierarchy for our assets and liabilities measured at fair value on a recurring and nonrecurring basis. In instances in which the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level of input that is significant to the fair value measurement in its entirety. Our assessment of the significance of the particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. We determine other than temporary impairment in real estate investments and debt and preferred equity investments, including intangibles primarily utilizing cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs. In January 2018, the partnership agreement for our investment in 919 Third Avenue was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $54.9 million fair value adjustment in the consolidated statement of operations. This fair value was determined using a third party valuation which primarily utilized cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs. The fair value of derivative instruments is based on current market data received from financial sources that trade such instruments and are based on prevailing market data and derived from third party proprietary models based on well-recognized financial principles and reasonable estimates about relevant future market conditions, which are classified as Level 2 inputs. The financial assets and liabilities that are not measured at fair value on our consolidated balance sheets include cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses, debt and preferred equity investments, mortgages and other loans payable and other secured and unsecured debt. The carrying amount of cash and cash equivalents, restricted cash, accounts receivable, and accounts payable and accrued expenses reported in our consolidated balance sheets approximates fair value due to the short term nature of these instruments. The fair value of debt and preferred equity investments, which is classified as Level 3, is estimated by discounting the future cash flows using current interest rates at which similar loans with the same maturities would be made to borrowers with similar credit ratings. The fair value of borrowings, which is classified as Level 3, is estimated by discounting the contractual cash flows of each debt instrument to their present value using adjusted market interest rates, which is provided by a third-party specialist.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of commercial office properties	As of September 30, 2018 , we owned the following interests in properties in the New York metropolitan area, primarily in midtown Manhattan. Our investments located outside of Manhattan are referred to as the Suburban properties: Location Type Number of Approximate Square Feet (unaudited) Weighted Average (1) (unaudited) Commercial: Manhattan Office (2)(3) 15 8,303,245 93.6 % Retail (4)(5) 5 364,816 98.9 % Development/Redevelopment 1 160,000 — % 21 8,828,061 92.2 % Suburban Office 6 1,432,400 93.8 % Retail 1 52,000 100.0 % 7 1,484,400 94.0 % Total commercial properties 28 10,312,461 92.4 % Residential: Manhattan Residential (4) — 222,855 95.8 % Total portfolio 28 10,535,316 92.5 % (1) The weighted average occupancy for commercial properties represents the total occupied square feet divided by total square footage at acquisition. The weighted average occupancy for residential properties represents the total occupied units divided by total available units. (2) Includes one unconsolidated joint venture property at 919 Third Avenue comprised of approximately 1,454,000 square feet. (3) Includes one unconsolidated tenancy-in-common (or "TIC") interest at 2 Herald Square, which is under contract for sale as of September 30, 2018 . (4) As of September 30, 2018 , we owned a building at 315 West 33rd Street, also known as The Olivia, that was comprised of approximately 270,132 square feet (unaudited) of retail space and approximately 222,855 square feet (unaudited) of residential space. For the purpose of this report, we have included this building in the number of retail properties we own. However, we have included only the retail square footage in the retail approximate square footage, and have listed the balance of the square footage as residential square footage. (5) Includes two unconsolidated joint venture retail properties at 131-137 Spring Street comprised of approximately 68,342 square feet.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases)	The following summarizes our identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases) as of September 30, 2018 and December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Identified intangible assets (included in other assets): Gross amount $ 213,421 $ 276,163 Accumulated amortization (199,668 ) (236,737 ) Net (1) $ 13,753 $ 39,426 Identified intangible liabilities (included in deferred revenue): Gross amount $ 230,275 $ 496,438 Accumulated amortization (214,804 ) (366,091 ) Net (1) $ 15,471 $ 130,347 (1) As of September 30, 2018 and December 31, 2017 , $0.0 million and $0.1 million , respectively and $0.0 million and $0.1 million , respectively, of net intangible assets and net intangible liabilities, were reclassified to assets held for sale and liabilities related to assets held for sale.

Properties Held for Sale and _2

Properties Held for Sale and Property Dispositions (Tables)	9 Months Ended
	Sep. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Summary Of Properties Sold	The following table summarizes the properties sold during the nine months ended September 30, 2018 : Property Disposition Date Property Type Approximate Square Feet Sales Price (1) (in millions) Gain (loss) (2) (in millions) 115-117 Stevens Avenue May 2018 Fee Interest 178,000 $ 12.0 $ (0.7 ) 635 Madison Avenue June 2018 Fee Interest 176,530 153.0 (14.1 ) 1-6 International Drive July 2018 Fee Interest 540,000 55.0 (2.6 ) (1) Sales price represents the gross sales price for a property or the gross asset valuation for interests in a property. (2) Gain (loss) on sale amounts do not include adjustments for expenses recorded in subsequent periods.

Debt and Preferred Equity Inv_2

Debt and Preferred Equity Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of debt and preferred equity book balance roll forward	Below is a summary of the activity relating to our debt and preferred equity investments for the nine months ended September 30, 2018 and the twelve months ended December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Balance at beginning of period (1) $ 2,114,041 $ 1,640,412 Debt investment originations/accretion (2) 664,961 1,142,591 Preferred equity investment originations/accretion (2) 6,305 144,456 Redemptions/sales/syndications/amortization (3) (808,250 ) (813,418 ) Balance at end of period (1) $ 1,977,057 $ 2,114,041 (1) Net of unamortized fees, discounts, and premiums. (2) Accretion includes amortization of fees and discounts and paid-in-kind investment income. (3) Certain participations in debt investments that were sold or syndicated did not meet the conditions for sale accounting are included in other assets and other liabilities on the consolidated balance sheets.
Summary of debt investments	As of September 30, 2018 and December 31, 2017 , we held the following debt investments with an aggregate weighted average current yield of 8.92% at September 30, 2018 (in thousands): Loan Type September 30, 2018 September 30, 2018 Senior September 30, 2018 (1) December 31, 2017 (1) Maturity Date (2) Fixed Rate Investments: Mezzanine Loan (3a) $ — $ 1,160,000 $ 210,832 $ 204,005 March 2020 Mezzanine Loan — 15,000 3,500 3,500 September 2021 Mezzanine Loan — 147,000 24,927 24,913 April 2022 Mezzanine Loan — 280,000 36,069 34,600 August 2022 Mezzanine Loan — 83,689 12,704 12,699 November 2023 Mezzanine Loan (3b) — 115,000 12,939 12,932 June 2024 Mezzanine Loan — 95,000 30,000 30,000 January 2025 Mezzanine Loan — 340,000 15,000 15,000 November 2026 Mezzanine Loan — 1,657,500 55,250 55,250 June 2027 Mortgage/Jr. Mortgage Loan (4) — — — 250,464 Mortgage Loan (5)(6) — — — 26,366 Loan Type September 30, 2018 September 30, 2018 Senior September 30, 2018 (1) December 31, 2017 (1) Maturity Date (2) Mortgage Loan (7) — — — 239 Total fixed rate $ — $ 3,893,189 $ 401,221 $ 669,968 Floating Rate Investments: Mezzanine Loan (8) — 20,523 10,977 10,934 August 2018 Mezzanine Loan (9) 2,325 45,025 35,168 34,879 October 2018 Mezzanine Loan (3c) — 150,000 15,368 15,381 December 2018 Mezzanine Loan (3d) — — 14,856 14,869 December 2018 Mezzanine Loan — 33,000 26,987 26,927 December 2018 Mezzanine Loan 3,607 30,438 10,403 8,550 January 2019 Mezzanine Loan (3e)(10) 795 — 15,150 15,148 March 2019 Mezzanine Loan — 38,000 21,977 21,939 March 2019 Mezzanine Loan (11) — 40,000 19,972 19,982 April 2019 Mezzanine Loan (11) — 37,891 18,380 34,947 April 2019 Mezzanine Loan — 175,000 37,404 37,250 April 2019 Mezzanine Loan — 265,000 24,928 24,830 April 2019 Mortgage/Jr. Mortgage Participation Loan 17,186 228,516 82,517 71,832 August 2019 Mortgage/Mezzanine Loan (12) — — 19,999 19,940 August 2019 Mezzanine Loan (13) — 65,000 14,998 14,955 August 2019 Mortgage/Mezzanine Loan 5,905 — 180,339 143,919 September 2019 Mezzanine Loan — 350,000 34,847 34,737 October 2019 Mortgage/Mezzanine Loan 387 — 39,338 — December 2019 Mortgage/Mezzanine Loan 13,048 — 56,624 43,845 January 2020 Mezzanine Loan 812 574,120 78,841 75,834 January 2020 Mortgage Loan 13,579 — 86,058 — February 2020 Mezzanine Loan 2,944 312,310 51,669 — March 2020 Mortgage/Mezzanine Loan 27,776 — 288,811 — April 2020 Mezzanine Loan 6,095 36,786 12,141 11,259 July 2020 Mezzanine Loan 41,309 355,148 85,955 75,428 November 2020 Mortgage and Mezzanine Loan 35,631 — 96,185 88,989 December 2020 Mortgage and Mezzanine Loan — — 35,236 35,152 December 2020 Jr. Mortgage Participation/Mezzanine Loan — 60,000 15,657 15,635 July 2021 Mortgage/Mezzanine Loan (14) — — — 162,553 Mortgage/Mezzanine Loan (14) — — — 74,755 Mortgage/Mezzanine Loan (15) — — — 23,609 Mezzanine Loan (16) — — — 12,174 Mezzanine Loan (17) — — — 37,851 Mezzanine Loan (17) — — — 14,855 Mortgage/Mezzanine Loan (6) — — — 16,969 Mezzanine Loan (7) — — — 59,723 Total floating rate $ 171,399 $ 2,816,757 $ 1,430,785 $ 1,299,650 Total $ 171,399 $ 6,709,946 $ 1,832,006 $ 1,969,618 (1) Carrying value is net of discounts, premiums, original issue discounts and deferred origination fees. (2) Represents contractual maturity, excluding any unexercised extension options. (3) Carrying value is net of the following amounts that were sold or syndicated, which are included in other assets and other liabilities on the consolidated balance sheets as a result of the transfers not meeting the conditions for sale accounting: (a) $1.3 million , (b) $12.0 million , (c) $14.6 million , (d) $14.1 million , and (e) $5.1 million . (4) These loans were conveyed to SL Green in the form of a distribution in March 2018. (5) In September 2014, we acquired a $26.4 million mortgage loan at a $0.2 million discount and a $5.7 million junior mortgage participation at a $5.7 million discount. The junior mortgage participation has been a nonperforming loan since acquisition, is currently on non-accrual status and has no carrying value. (6) This loan was repaid in August 2018. (7) This loan was repaid in September 2018. (8) This loan was conveyed to SL Green in the form of a distribution in October 2018. (9) This loan was extended in October 2018. (10) This loan was extended in March 2018. (11) This loan was extended in April 2018. (12) This loan was extended in August 2018. (13) This loan was extended in July 2018. (14) This loan was repaid in February 2018. (15) This loan was sold in May 2018. (16) This loan was conveyed to SL Green in the form of a distribution in July 2018. (17) This loan was repaid in July 2018.
Schedule of preferred equity investments	As of September 30, 2018 and December 31, 2017 , we held the following preferred equity investments with an aggregate weighted average current yield of 5.73% at September 30, 2018 (in thousands): Type September 30, 2018 September 30, 2018 Senior September 30, 2018 (1) December 31, 2017 (1) Maturity (2) Preferred Equity $ — $ 272,000 $ 145,051 $ 144,423 April 2021 Total $ — $ 272,000 $ 145,051 $ 144,423 (1) Carrying value is net of deferred origination fees. (2) Represents contractual maturity, excluding any unexercised extension options.

Investments in Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Tables)	9 Months Ended
	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Schedule of general information on joint ventures	The table below provides general information on each of our joint ventures as of September 30, 2018 : Property Partner Ownership Interest (1) Economic Interest (1) Unaudited Approximate Square Feet Acquisition Date (2) Acquisition Price (2) (in thousands) 919 Third Avenue (3) New York State Teacher's Retirement System 51.00% 51.00% 1,454,000 January 2007 $ 1,256,727 131-137 Spring Street Invesco Real Estate 20.00% 20.00% 68,342 August 2015 277,750 2 Herald Square (4) (4) 49.00% 49.00% 369,000 May 2018 266,000 (1) Ownership interest and economic interest represent the Company's interests in the joint venture as of September 30, 2018 . Changes in ownership or economic interests within the current year are disclosed in the notes below. (2) Acquisition date and price represent the date on which the Company initially acquired an interest in the joint venture and the actual or implied gross purchase price for the joint venture on that date. Acquisition date and price are not adjusted for subsequent acquisitions or dispositions of interest. (3) In January 2018, the partnership agreement for our investment was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $54.9 million fair value adjustment in the consolidated statement of operations. This fair value was allocated to the assets and liabilities, including identified intangibles of the property. (4) In May 2018, SL Green assigned the Company a 49.0% tenancy-in-common interest in the leasehold interest in 2 Herald Square and entered into an agreement to sell this investment. Consolidation of this investment is not required as such interest does not qualify as a VIE and does not meet the control requirement for consolidation. Accordingly, we account for this investment using the equity method of accounting. We use the equity method of accounting because the shared decision-making involved in a tenancy-in-common interest investment provides us with significant influence on the operating and financial decisions of this investment. As of September 30, 2018 and December 31, 2017 , the carrying value for acquisition, development and construction arrangements were as follows (in thousands): Loan Type September 30, 2018 December 31, 2017 Maturity Date Mezzanine Loan (1) $ — $ 26,716 Mezzanine Loan and Preferred Equity (2) — 100,000 $ — $ 126,716 (1) The Company was redeemed on this investment in July 2018. (2) The mezzanine loan was repaid and the preferred equity interest was redeemed in March 2018.
Schedule of first mortgage notes payable collateralized by the respective joint venture properties and assignment of leases	The first mortgage notes and other loans payable collateralized by the respective joint venture properties and assignment of leases at September 30, 2018 and December 31, 2017 , respectively, are as follows (amounts in thousands): Property Economic Interest (1) Maturity Date Interest Rate (2) September 30, 2018 December 31, 2017 Fixed Rate Debt: 919 Third Avenue 51.00 % June 2023 5.12 % $ 500,000 $ — Floating Rate Debt: 131-137 Spring Street 20.00 % August 2020 L+ 1.55 % $ 141,000 $ 141,000 Total joint venture mortgages and other loans payable $ 641,000 $ 141,000 Deferred financing costs, net (2,031 ) (2,862 ) Total joint venture mortgages and other loans payable, net $ 638,969 $ 138,138 (1) Economic interest represents the Company's interests in the joint venture as of September 30, 2018 . Changes in ownership or economic interests, if any, within the current year are disclosed in the notes to the investment in unconsolidated joint ventures table above. (2) Interest rates as of September 30, 2018 . Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified.
Schedule of combined balance sheets for the unconsolidated joint ventures	he combined balance sheets for the unconsolidated joint ventures at September 30, 2018 and December 31, 2017 are as follows (in thousands): September 30, 2018 December 31, 2017 Assets (1) Commercial real estate property, net $ 1,860,269 $ 273,116 Debt and preferred equity investments, net — 141,716 Other assets 773,530 15,735 Total assets $ 2,633,799 $ 430,567 Liabilities and members' equity (1) Mortgages and other loans payable, net $ 638,969 $ 138,138 Other liabilities 895,127 18,908 Members' equity 1,099,703 273,521 Total liabilities and members' equity $ 2,633,799 $ 430,567 Company's investments in unconsolidated joint ventures $ 477,686 $ 130,217 (1) The combined assets, liabilities and equity for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.
Schedule of combined statements of operations for the unconsolidated joint ventures	he combined balance sheets for the unconsolidated joint ventures at September 30, 2018 and December 31, 2017 are as follows (in thousands): September 30, 2018 December 31, 2017 Assets (1) Commercial real estate property, net $ 1,860,269 $ 273,116 Debt and preferred equity investments, net — 141,716 Other assets 773,530 15,735 Total assets $ 2,633,799 $ 430,567 Liabilities and members' equity (1) Mortgages and other loans payable, net $ 638,969 $ 138,138 Other liabilities 895,127 18,908 Members' equity 1,099,703 273,521 Total liabilities and members' equity $ 2,633,799 $ 430,567 Company's investments in unconsolidated joint ventures $ 477,686 $ 130,217 (1) The combined assets, liabilities and equity for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018. The combined statements of operations for the unconsolidated joint ventures for the three and nine months ended September 30, 2018 and 2017 are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Total revenues $ 42,037 $ 7,340 $ 112,399 $ 26,934 Operating expenses 6,659 182 18,925 636 Real estate taxes 9,178 381 22,674 1,013 Ground rent 3,106 — 3,106 — Interest expense, net of interest income 10,377 1,025 24,174 2,759 Amortization of deferred financing costs 277 283 831 837 Depreciation and amortization 12,607 2,102 37,701 6,304 Total expenses $ 42,204 $ 3,973 $ 107,411 $ 11,549 Net (loss) income (1) $ (167 ) $ 3,367 $ 4,988 $ 15,385 Company's equity in net income from unconsolidated joint ventures (1) $ (164 ) $ 2,927 $ 3,835 $ 10,362 (1) The combined statements of operation and the Company's equity in net income for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.
Discontinued Operations, Disposed of by Sale
Schedule of Equity Method Investments [Line Items]
Schedule of general information on joint ventures	The following table summarizes the investments in unconsolidated joint ventures disposed of during the nine months ended September 30, 2018 : Property Ownership Interest Disposition Date Type of Sale Gross Asset Valuation (in thousands) (1) Gain (Loss) on Sale (in thousands) (2) Mezzanine Loan (3) 33.33% August 2018 Repayment $ 15,000 N/A (1) Represents implied gross valuation for the joint venture or sales price of the property. (2) Represents the Company's share of the gain (loss). (3) Our investment in a joint venture that owned a mezzanine loan secured by a commercial property in midtown Manhattan was repaid after the joint venture received repayment of the underlying loan.

Mortgages and Other Loans Pay_2

Mortgages and Other Loans Payable (Tables)	9 Months Ended
	Sep. 30, 2018
Mortgage Note and Other Loans Payable
Schedule of the first mortgage note and other loans payable collateralized by the property, assignment of leases and investment	The first mortgages and other loans payable collateralized by the respective properties and assignment of leases or debt investments at September 30, 2018 and December 31, 2017 , respectively, were as follows (amounts in thousands): Property Maturity Date Interest Rate (1) September 30, 2018 December 31, 2017 Fixed Rate Debt: 315 West 33rd Street February 2027 4.24 % $ 250,000 $ 250,000 919 Third Avenue (2) — 500,000 Floating Rate Debt: 2017 Master Repurchase Agreement June 2019 L+ 2.34 % $ 300,000 $ 90,809 115 Spring Street September 2023 L+ 3.40 % 65,550 — Total mortgages and other loans payable $ 615,550 $ 840,809 Deferred financing costs, net of amortization (8,489 ) (11,161 ) Total mortgages and other loans payable, net $ 607,061 $ 829,648 (1) Interest rate as of September 30, 2018 . Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified. (2) Our investment in the property was deconsolidated as of January 1, 2018. See Note 6, "Investments in Unconsolidated Joint Ventures".

Corporate Indebtedness (Tables)

Corporate Indebtedness (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of senior unsecured notes and other related disclosures by scheduled maturity date	The following table sets forth our senior unsecured notes and other related disclosures as of September 30, 2018 and December 31, 2017 , respectively, by scheduled maturity date (amounts in thousands): Issuance September 30, September 30, December 31, Coupon (1) Initial Maturity Date March 16, 2010 (2) $ 250,000 $ 250,000 $ 250,000 7.75 % 10 March 2020 November 15, 2012 (3) 300,000 304,421 305,163 4.50 % 10 December 2022 December 17, 2015 (2) 100,000 100,000 100,000 4.27 % 10 December 2025 August 5, 2011 (2) (4) — — 249,953 $ 650,000 $ 654,421 $ 905,116 Deferred financing costs, net (3,081 ) (4,049 ) $ 650,000 $ 651,340 $ 901,067 (1) Interest on the senior unsecured notes is payable semi-annually with principal and unpaid interest due on the scheduled maturity dates. (2) Issued by SL Green, the Operating Partnership and ROP, as co-obligors. (3) In October 2017, SL Green, the Operating Partnership, and ROP, as co-obligors, issued an additional $100.0 million of 4.50% senior unsecured notes due December 2022. The notes were priced at 105.334% . (4) Balance was repaid in August 2018.
Schedule of combined aggregate principal maturities of mortgage and other loans payable, 2012 credit facility and senior unsecured notes, including as-of-right extension options	Combined aggregate principal maturities of mortgages and other loans payable, and senior unsecured notes as of September 30, 2018 , including as-of-right extension options and put options, were as follows (in thousands): Scheduled Principal Senior Unsecured Notes Total Remaining 2018 $ — $ — $ — $ — 2019 — — — — 2020 — 300,000 250,000 550,000 2021 — — — — 2022 — — 300,000 300,000 Thereafter — 315,550 100,000 415,550 $ — $ 615,550 $ 650,000 $ 1,265,550
Schedule of consolidated interest expense, excluding capitalized interest	Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest expense before capitalized interest $ 17,052 $ 34,658 $ 51,729 $ 96,740 Interest capitalized (1,594 ) (31 ) (3,908 ) (533 ) Interest income — — (3 ) (5 ) Interest expense, net $ 15,458 $ 34,627 $ 47,818 $ 96,202

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	The following table provides the carrying value and fair value of these financial instruments as of September 30, 2018 and December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Carrying Value (1) Fair Value Carrying Value (1) Fair Value Debt and preferred equity investments $ 1,977,057 (2) $ 2,114,041 (2) Fixed rate debt $ 904,421 $ 907,337 $ 1,655,116 $ 1,715,501 Variable rate debt 365,550 382,438 90,809 92,087 $ 1,269,971 $ 1,289,775 $ 1,745,925 $ 1,807,588 (1) Amounts exclude net deferred financing costs. (2) At September 30, 2018 , debt and preferred equity investments had an estimated fair value ranging between $2.0 billion and $2.2 billion . At December 31, 2017 , debt and preferred equity investments had an estimated fair value ranging between $2.1 billion and $2.3 billion .

Financial Instruments_ Deriva_2

Financial Instruments: Derivatives and Hedging (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of effect of derivative financial instruments on consolidated statements of income	The following table presents the effect of our derivative financial instruments that are designated and qualify as hedging instruments on the consolidated statements of operations for the three months ended September 30, 2018 and 2017 , respectively (in thousands): Amount of Loss Recognized in Other Comprehensive Loss (Effective Portion) Location of Loss Reclassified from Accumulated Other Comprehensive Loss into Income Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Location of Gain Recognized in Income on Derivative Amount of Gain Recognized into Income (Ineffective Portion) Three Months Ended September 30, Three Months Ended September 30, Three Months Ended September 30, Derivative 2018 2017 2018 2017 2018 2017 Interest Rate Swap $ — $ — Interest expense $ — $ 89 Interest expense $ — $ — The following table presents the effect of our derivative financial instruments that are designated and qualify as hedging instruments on the consolidated statements of operations for the nine months ended September 30, 2018 and 2017 , respectively (in thousands): Amount of Loss Recognized in Other Comprehensive Loss (Effective Portion) Location of Loss Reclassified from Accumulated Other Comprehensive Loss into Income Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Location of Gain Recognized in Income on Derivative Amount of Gain Recognized into Income (Ineffective Portion) Nine Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, Derivative 2018 2017 2018 2017 2018 2017 Interest Rate Swap $ — $ — Interest expense $ — $ 269 Interest expense $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum lease payments under capital leases and noncancellable operating leases	The following is a schedule of future minimum lease payments under non-cancellable operating leases with initial terms in excess of one year as of September 30, 2018 (in thousands): Non-cancellable operating leases Remaining 2018 $ 4,934 2019 19,736 2020 19,736 2021 19,886 2022 17,730 2023 15,424 Thereafter 237,011 Total minimum lease payments $ 334,457

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of selected results of operations and selected asset information	Selected consolidated results of operations for the three and nine months ended September 30, 2018 and 2017 , and selected asset information as of September 30, 2018 and December 31, 2017 , regarding our operating segments are as follows (in thousands): Real Estate Segment Debt and Preferred Equity Segment Total Company Total revenues: Three months ended: September 30, 2018 $ 149,462 $ 49,125 $ 198,587 September 30, 2017 193,962 47,946 241,908 Nine months ended: September 30, 2018 $ 472,777 $ 143,087 $ 615,864 September 30, 2017 577,151 148,924 726,075 Net income Three months ended: September 30, 2018 $ 39,354 $ 34,154 $ 73,508 September 30, 2017 24,722 39,988 64,710 Nine months ended: September 30, 2018 $ 172,068 $ 100,866 $ 272,934 September 30, 2017 7,342 131,507 138,849 Total assets As of: September 30, 2018 $ 5,204,346 $ 2,100,202 $ 7,304,548 December 31, 2017 6,182,431 2,359,077 8,541,508

Organization and Basis of Pre_3

Organization and Basis of Presentation (Details) $ in Billions	9 Months Ended
	Sep. 30, 2018USD ($)ft²property
Real estate properties
Percentage of ownership in SL Green Operating Partnership owned by SL Green Realty Corp (as a percent)	94.90%
Number of Properties | property	28
Approximate Square Feet (sqft)	10,535,316
Weighted Average Occupancy (as a percent)	92.50%
Debt and preferred equity investments including investments held by unconsolidated joint ventures | $	$ 2
Manhattan
Real estate properties
Number of Properties | property	21
Approximate Square Feet (sqft)	8,828,061
Weighted Average Occupancy (as a percent)	92.20%
Suburban
Real estate properties
Number of Properties | property	7
Approximate Square Feet (sqft)	1,484,400
Weighted Average Occupancy (as a percent)	94.00%
Office | Manhattan
Real estate properties
Number of Properties | property	15
Approximate Square Feet (sqft)	8,303,245
Weighted Average Occupancy (as a percent)	93.60%
Office | Suburban
Real estate properties
Number of Properties | property	6
Approximate Square Feet (sqft)	1,432,400
Weighted Average Occupancy (as a percent)	93.80%
Retail | 919 Third Avenue
Real estate properties
Approximate Square Feet (sqft)	1,454,000
Number of unconsolidated joint venture properties | property	1
Retail | 2 Herald Square
Real estate properties
Number of unconsolidated joint venture properties | property	1
Retail | 131-137 Spring Street
Real estate properties
Approximate Square Feet (sqft)	68,342
Number of unconsolidated joint venture properties | property	2
Retail | Manhattan
Real estate properties
Number of Properties | property	5
Approximate Square Feet (sqft)	364,816
Weighted Average Occupancy (as a percent)	98.90%
Retail | Suburban
Real estate properties
Number of Properties | property	1
Approximate Square Feet (sqft)	52,000
Weighted Average Occupancy (as a percent)	100.00%
Development Properties | Manhattan
Real estate properties
Number of Properties | property	1
Approximate Square Feet (sqft)	160,000
Weighted Average Occupancy (as a percent)	0.00%
Commercial
Real estate properties
Number of Properties | property	28
Approximate Square Feet (sqft)	10,312,461
Weighted Average Occupancy (as a percent)	92.40%
Residential | Manhattan
Real estate properties
Number of Properties | property	0
Approximate Square Feet (sqft)	222,855
Weighted Average Occupancy (as a percent)	95.80%
Dual property type, retail portion
Real estate properties
Approximate Square Feet (sqft)	270,132
Dual property type, residential portion
Real estate properties
Approximate Square Feet (sqft)	222,855

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2019	Dec. 31, 2017
Investment in Commercial Real Estate Properties
Depreciable real estate reserves	$ 0	$ (379,000)	$ 0	$ (85,707,000)
Increase in rental revenue from amortization of acquired leases	1,300,000	4,300,000	5,500,000	12,700,000
Loan reserves	0	$ 0	0	$ 0
Increase in total assets	7,304,548,000		7,304,548,000			$ 8,541,508,000
Increase in total liabilities	1,444,806,000		1,444,806,000			2,099,327,000
Identified intangible assets (included in other assets):
Gross amount	213,421,000		213,421,000			276,163,000
Accumulated amortization	(199,668,000)		(199,668,000)			(236,737,000)
Net	13,753,000		13,753,000			39,426,000
Identified intangible liabilities (included in deferred revenue):
Gross amount	230,275,000		230,275,000			496,438,000
Accumulated amortization	(214,804,000)		(214,804,000)			(366,091,000)
Net	15,471,000		15,471,000			130,347,000
Net Intangible Assets Transferred to Assets Held for Sale	0		0			100,000
Net Intangible Liabilities Transferred to Liabilities Related to Assets Held for Sale	$ 0		$ 0			$ 100,000
Above-market leases | Minimum
Investment in Commercial Real Estate Properties
Estimated useful life of intangible assets (years)			1 year
Above-market leases | Maximum
Investment in Commercial Real Estate Properties
Estimated useful life of intangible assets (years)			14 years
Below-market leases | Minimum
Investment in Commercial Real Estate Properties
Estimated useful life of intangible assets (years)			1 year
Below-market leases | Maximum
Investment in Commercial Real Estate Properties
Estimated useful life of intangible assets (years)			14 years
In-place leases | Minimum
Investment in Commercial Real Estate Properties
Estimated useful life of intangible assets (years)			1 year
In-place leases | Maximum
Investment in Commercial Real Estate Properties
Estimated useful life of intangible assets (years)			14 years
Building | Minimum
Investment in Commercial Real Estate Properties
Estimated useful life (years)			3 years
Building | Maximum
Investment in Commercial Real Estate Properties
Estimated useful life (years)			40 years
Accounting Standards Update 2016-02 | Scenario, Forecast | Minimum
Investment in Commercial Real Estate Properties
Increase in total assets					$ 100,000,000
Increase in total liabilities					100,000,000
Accounting Standards Update 2016-02 | Scenario, Forecast | Maximum
Investment in Commercial Real Estate Properties
Increase in total assets					200,000,000
Increase in total liabilities					$ 200,000,000

Significant Accounting Polici_5

Significant Accounting Policies - Concentrations of Credit Risk/Reclassification (Details) - Annualized cash rent - Customer concentration	3 Months Ended
	Sep. 30, 2018
Concentrations of Credit Risk
Maximum percentage of annualized cash rent for any one tenant not individually disclosed	5.00%
1185 Avenue of the Americas
Concentrations of Credit Risk
Percentage of concentration	14.70%
625 Madison Avenue
Concentrations of Credit Risk
Percentage of concentration	11.00%
919 Third Avenue
Concentrations of Credit Risk
Percentage of concentration	8.70%
750 Third Avenue
Concentrations of Credit Risk
Percentage of concentration	8.40%
810 Seventh Avenue
Concentrations of Credit Risk
Percentage of concentration	8.20%
555 W. 57th Street
Concentrations of Credit Risk
Percentage of concentration	7.60%
125 Park Avenue
Concentrations of Credit Risk
Percentage of concentration	7.40%
1350 Avenue of the Americas
Concentrations of Credit Risk
Percentage of concentration	7.10%
711 Third Avenue
Concentrations of Credit Risk
Percentage of concentration	5.80%

Properties Held for Sale and _3

Properties Held for Sale and Property Dispositions (Details) $ in Millions	1 Months Ended
	Jul. 31, 2018USD ($)ft²	Jun. 30, 2018USD ($)ft²	May 31, 2018USD ($)ft²	Sep. 30, 2018ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Approximate Square Feet | ft²				10,535,316
115-117 Stevens Avenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Approximate Square Feet | ft²			178,000
Sales price			$ 12
Gain (loss) on sale			$ (0.7)
635 Madison Avenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Approximate Square Feet | ft²		176,530
Sales price		$ 153
Gain (loss) on sale		$ (14.1)
1-6 International Drive
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Approximate Square Feet | ft²	540,000
Sales price	$ 55
Gain (loss) on sale	$ (2.6)

Debt and Preferred Equity Inv_3

Debt and Preferred Equity Investments - Debt and Preferred Equity Investment Rollforward (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of period	$ 2,114,041	$ 1,640,412
Redemptions/Sales/Syndications/Amortization	(808,250)	(813,418)
Balance at end of period	1,977,057	2,114,041
Debt Investments in Mortgage Loans
Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	664,961	1,142,591
Preferred Equity Investments in Mortgage Loans
Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	$ 6,305	$ 144,456

Debt and Preferred Equity Inv_4

Debt and Preferred Equity Investments (Details)	1 Months Ended		9 Months Ended	12 Months Ended
	May 31, 2018	Sep. 30, 2014USD ($)	Sep. 30, 2018USD ($)segment	Dec. 31, 2017USD ($)segment
Mortgage Loans on Real Estate [Line Items]
Interest rate (as a percent)			8.92%
Debt Investments Held [Abstract]
Carrying Value			$ 1,977,057,000	$ 2,114,041,000
Number of portfolio segments | segment			1	1
Financing receivables included in other assets			$ 111,500,000	$ 93,400,000
Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Amount participated out			1,300,000
Mezzanine Loan with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Amount participated out			12,000,000
Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Amount participated out			14,600,000
Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Amount participated out			14,100,000
Mezzanine Loan with an Initial Maturity of March 2019
Debt Investments Held [Abstract]
Amount participated out			5,100,000
Debt Investments in Mortgage Loans
Debt Investments Held [Abstract]
Future Funding Obligations			171,399,000
Senior Financing			6,709,946,000
Carrying Value			$ 1,832,006,000	1,969,618,000
Preferred Equity Investments in Mortgage Loans
Mortgage Loans on Real Estate [Line Items]
Interest rate (as a percent)			5.73%
Debt Investments Held [Abstract]
Future Funding Obligations			$ 0
Senior Financing			272,000,000
Carrying Value			145,051,000	144,423,000
Preferred Equity, April 2021
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			272,000,000
Carrying Value			145,051,000	144,423,000
Junior Mortgage Participation Acquired in September 2014
Mortgage Loans on Real Estate [Line Items]
Payments to acquire loans receivable		$ 0
Debt Investments Held [Abstract]
Carrying Value				0
Fixed Rate Investments
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			3,893,189,000
Carrying Value			401,221,000	669,968,000
Fixed Rate Investments | Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			1,160,000,000
Carrying Value			210,832,000	204,005,000
Fixed Rate Investments | Mezzanine Loan, September 2021
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			15,000,000
Carrying Value			3,500,000	3,500,000
Fixed Rate Investments | Mezzanine Loan with an Initial Maturity Date of April 2022
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			147,000,000
Carrying Value			24,927,000	24,913,000
Fixed Rate Investments | Mezzanine Loan with an Initial Maturity of August 2022
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			280,000,000
Carrying Value			36,069,000	34,600,000
Fixed Rate Investments | Mezzanine Loan, with an Initial Maturity Date of November 2023
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			83,689,000
Carrying Value			12,704,000	12,699,000
Fixed Rate Investments | Mezzanine Loan with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			115,000,000
Carrying Value			12,939,000	12,932,000
Fixed Rate Investments | Mezzanine Loan, with an Initial Maturity Date of January 2025
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			95,000,000
Carrying Value			30,000,000	30,000,000
Fixed Rate Investments | Mezzanine Loan with an Initial Maturity Date of November 2026
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			340,000,000
Carrying Value			15,000,000	15,000,000
Fixed Rate Investments | Mezzanine Loan with an Initial Maturity Date of June 2027
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			1,657,500,000
Carrying Value			55,250,000	55,250,000
Fixed Rate Investments | Mortgage and Jr Mortgage loan satisfied via foreclosure
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	250,464,000
Fixed Rate Investments | Mezzanine Loan Repaid In August 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	26,366,000
Fixed Rate Investments | Mortgage Loan Repaid In September 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	239,000
Fixed Rate Investments | Mortgage Loan With An Initial Maturity Date Of February 2019
Debt Investments Held [Abstract]
Loan acquired		26,400,000
Discount on loan acquired		200,000
Fixed Rate Investments | Junior Mortgage Participation, Related To Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Loan acquired		5,700,000
Discount on loan acquired		$ 5,700,000
Floating Rate Investments
Debt Investments Held [Abstract]
Future Funding Obligations			171,399,000
Senior Financing			2,816,757,000
Carrying Value			1,430,785,000	1,299,650,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations			2,944,000
Senior Financing			312,310,000
Carrying Value			51,669,000	0
Floating Rate Investments | Mezzanine Loan, August 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			20,523,000
Carrying Value			10,977,000	10,934,000
Floating Rate Investments | Mezzanine Loan, October 2018
Debt Investments Held [Abstract]
Future Funding Obligations			2,325,000
Senior Financing			45,025,000
Carrying Value			35,168,000	34,879,000
Floating Rate Investments | Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			150,000,000
Carrying Value			15,368,000	15,381,000
Floating Rate Investments | Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			14,856,000	14,869,000
Floating Rate Investments | Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			33,000,000
Carrying Value			26,987,000	26,927,000
Floating Rate Investments | Mezzanine Loan, January 2019
Debt Investments Held [Abstract]
Future Funding Obligations			3,607,000
Senior Financing			30,438,000
Carrying Value			10,403,000	8,550,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity of March 2019
Debt Investments Held [Abstract]
Future Funding Obligations			795,000
Senior Financing			0
Carrying Value			15,150,000	15,148,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity of March 2019, 2
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			38,000,000
Carrying Value			21,977,000	21,939,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity Date of April 2019
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			40,000,000
Carrying Value			19,972,000	19,982,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity Date of April 2019
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			37,891,000
Carrying Value			18,380,000	34,947,000
Floating Rate Investments | Mezzanine Loan With An Initial Maturity Date Of April 2019, 3
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			175,000,000
Carrying Value			37,404,000	37,250,000
Floating Rate Investments | Mezzanine Loan With An Initial Maturity Date Of April 2019, 4
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			265,000,000
Carrying Value			24,928,000	24,830,000
Floating Rate Investments | Mortgage/Jr Mortgage Participate Loan, Maturity Date of August 2019
Debt Investments Held [Abstract]
Future Funding Obligations			17,186,000
Senior Financing			228,516,000
Carrying Value			82,517,000	71,832,000
Floating Rate Investments | Mortgage/Mezzanine Loan With An Initial Maturity Date Of August 2019
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			19,999,000	19,940,000
Floating Rate Investments | Mezzanine Loan With An Initial Maturity Date Of August 2019
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			65,000,000
Carrying Value			14,998,000	14,955,000
Floating Rate Investments | Mortgage/Mezzanine Loan with an Initial Maturity of September 2019
Debt Investments Held [Abstract]
Future Funding Obligations			5,905,000
Senior Financing			0
Carrying Value			180,339,000	143,919,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity of October 2019
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			350,000,000
Carrying Value			34,847,000	34,737,000
Floating Rate Investments | Mortgage/Mezzanine Loan with an Initial Maturity Date of December 2019
Debt Investments Held [Abstract]
Future Funding Obligations			387,000
Senior Financing			0
Carrying Value			39,338,000	0
Floating Rate Investments | Mortgage/Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations			13,048,000
Senior Financing			0
Carrying Value			56,624,000	43,845,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations			812,000
Senior Financing			574,120,000
Carrying Value			78,841,000	75,834,000
Floating Rate Investments | Mortgage Loan with an Initial Maturity of February 2020
Debt Investments Held [Abstract]
Future Funding Obligations			13,579,000
Senior Financing			0
Carrying Value			86,058,000	0
Floating Rate Investments | Mortgage and Mezzanine Loan with an Initial Maturity Date of April 2020
Debt Investments Held [Abstract]
Future Funding Obligations			27,776,000
Senior Financing			0
Carrying Value			288,811,000	0
Floating Rate Investments | Mezzanine Loan with an Initial Maturity of July 2020
Debt Investments Held [Abstract]
Future Funding Obligations			6,095,000
Senior Financing			36,786,000
Carrying Value			12,141,000	11,259,000
Floating Rate Investments | Mezzanine Loan with an Initial Maturity of November 2020
Debt Investments Held [Abstract]
Future Funding Obligations			41,309,000
Senior Financing			355,148,000
Carrying Value			85,955,000	75,428,000
Floating Rate Investments | Mortgage/Mezzanine Loan with an Initial Maturity of December 2020
Debt Investments Held [Abstract]
Future Funding Obligations			35,631,000
Senior Financing			0
Carrying Value			96,185,000	88,989,000
Floating Rate Investments | Mortgage/Mezzanine Loan with an Initial Maturity of December 2020, 2
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			35,236,000	35,152,000
Floating Rate Investments | Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			60,000,000
Carrying Value			15,657,000	15,635,000
Floating Rate Investments | Mortgage/Mezzanine Loan Repaid In February 2018, 2
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	162,553,000
Floating Rate Investments | Mortgage/Mezzanine Loan repaid in February 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	74,755,000
Floating Rate Investments | Mortgage/Mezzanine Loan Sold In May 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	23,609,000
Floating Rate Investments | Mezzanine Loan Exchanged For Property In July 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	12,174,000
Floating Rate Investments | Mezzanine Loan Repaid In July 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	37,851,000
Floating Rate Investments | Mezzanine Loan Repaid In July 2018, 2
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	14,855,000
Floating Rate Investments | Mortgage/Mezzanine Loan Repaid In August 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			0	16,969,000
Floating Rate Investments | Mezzanine Loan Repaid In September 2018
Debt Investments Held [Abstract]
Future Funding Obligations			0
Senior Financing			0
Carrying Value			$ 0	$ 59,723,000
2 Herald Square
Debt Investments Held [Abstract]
Tenancy in common interest, percent	49.00%

Investments in Unconsolidated_3

Investments in Unconsolidated Joint Ventures - Additional Information (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2018	Sep. 30, 2018USD ($)ft²	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)ft²	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Unaudited Approximate Square Feet (sqft) | ft²		10,535,316		10,535,316
Purchase price and other fair value adjustments		$ 0	$ 0	$ 54,860	$ 0
Acquisition, development and construction arrangements, carrying value		0		0		$ 126,716
Mezzanine Loan Due July 2036
Schedule of Equity Method Investments [Line Items]
Acquisition, development and construction arrangements, carrying value		0		0		26,716
Mezzanine Loans And Preferred Equity
Schedule of Equity Method Investments [Line Items]
Acquisition, development and construction arrangements, carrying value		$ 0		$ 0		$ 100,000
Joint Venture | 919 Third Avenue
Schedule of Equity Method Investments [Line Items]
Ownership Interest (as a percent)		51.00%		51.00%
Economic Interest (as a percent)		51.00%		51.00%
Unaudited Approximate Square Feet (sqft) | ft²		1,454,000		1,454,000
Acquisition Price		$ 1,256,727		$ 1,256,727
Joint Venture | 131-137 Spring Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest (as a percent)		20.00%		20.00%
Economic Interest (as a percent)		20.00%		20.00%
Unaudited Approximate Square Feet (sqft) | ft²		68,342		68,342
Acquisition Price		$ 277,750		$ 277,750
Joint Venture | 2 Herald Square
Schedule of Equity Method Investments [Line Items]
Ownership Interest (as a percent)		49.00%		49.00%
Economic Interest (as a percent)		49.00%		49.00%
Unaudited Approximate Square Feet (sqft) | ft²		369,000		369,000
Acquisition Price		$ 266,000		$ 266,000
Joint Venture | 919 Third Avenue | 919 Third Avenue
Schedule of Equity Method Investments [Line Items]
Purchase price and other fair value adjustments				$ 54,900
2 Herald Square
Schedule of Equity Method Investments [Line Items]
Tenancy in common interest, percent	49.00%

Investments in Unconsolidated_4

Investments in Unconsolidated Joint Ventures - Mortgages and Loans Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
919 Third Avenue
Schedule of Equity Method Investments [Line Items]
Fixed rate debt	$ 0	$ 500,000
Joint Venture
Schedule of Equity Method Investments [Line Items]
Total joint venture mortgages and other loans payable	641,000	141,000
Deferred financing costs, net	(2,031)	(2,862)
Total joint venture mortgages and other loans payable, net	$ 638,969	138,138
Joint Venture | 919 Third Avenue
Schedule of Equity Method Investments [Line Items]
Economic Interest (as a percent)	51.00%
Interest rate (as a percent)	5.12%
Fixed rate debt	$ 500,000	0
Joint Venture | 131-137 Spring Street
Schedule of Equity Method Investments [Line Items]
Economic Interest (as a percent)	20.00%
Floating rate debt	$ 141,000	$ 141,000
Joint Venture | Weighted Average | 131-137 Spring Street
Schedule of Equity Method Investments [Line Items]
Interest rate (as a percent)	1.55%

Investments in Unconsolidated_5

Investments in Unconsolidated Joint Ventures - Disposition of Joint Venture Interests or Properties (Details) - Mezzanine Loan $ in Thousands	Aug. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Ownership Interest	33.33%
Gross Asset Valuation	$ 15,000

Investments in Unconsolidated_6

Investments in Unconsolidated Joint Ventures - Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Assets
Commercial real estate property, net	$ 4,265,240		$ 4,265,240		$ 5,536,852
Other assets	230,040		230,040		245,598
Liabilities and members' equity
Mortgages and other loans payable, net	607,061		607,061		829,648
Other liabilities	58,231		58,231		92,514
Company's investments in unconsolidated joint ventures	477,686		477,686		130,217
Combined statements of income for the unconsolidated joint ventures
Real estate taxes	33,500	$ 40,610	98,045	$ 118,232
Ground rent	4,759	5,236	15,068	15,706
Amortization of deferred financing costs	721	2,580	3,777	6,706
Depreciation and amortization	41,867	53,549	125,163	156,106
Total expenses	128,487	180,142	389,971	517,213
Company's equity in net income from unconsolidated joint ventures	(164)	2,927	3,835	10,362
Joint Venture
Assets
Commercial real estate property, net	1,860,269		1,860,269		273,116
Debt and preferred equity investments, net	0		0		141,716
Other assets	773,530		773,530		15,735
Total assets	2,633,799		2,633,799		430,567
Liabilities and members' equity
Mortgages and other loans payable, net	638,969		638,969		138,138
Other liabilities	895,127		895,127		18,908
Members' equity	1,099,703		1,099,703		273,521
Total liabilities and members' equity	2,633,799		2,633,799		430,567
Company's investments in unconsolidated joint ventures	477,686		477,686		$ 130,217
Combined statements of income for the unconsolidated joint ventures
Total revenues	42,037	7,340	112,399	26,934
Operating expenses	6,659	182	18,925	636
Real estate taxes	9,178	381	22,674	1,013
Ground rent	3,106	0	3,106	0
Interest expense, net of interest income	10,377	1,025	24,174	2,759
Amortization of deferred financing costs	277	283	831	837
Depreciation and amortization	12,607	2,102	37,701	6,304
Total expenses	42,204	3,973	107,411	11,549
Net income	(167)	3,367	4,988	15,385
Company's equity in net income from unconsolidated joint ventures	$ (164)	$ 2,927	$ 3,835	$ 10,362

Mortgages and Other Loans Pay_3

Mortgages and Other Loans Payable (Details)	Dec. 06, 2015USD ($)	Sep. 30, 2018USD ($)extensiondebt_instrument	Apr. 30, 2018USD ($)	Dec. 31, 2017USD ($)	Jul. 31, 2016USD ($)
Mortgage note and other loan payable
Total mortgages and other loans payable		$ 615,550,000		$ 840,809,000
Deferred financing costs, net of amortization		(8,489,000)		(11,161,000)
Total mortgages and other loans payable, net		607,061,000		829,648,000
Debt and preferred equity investments		$ 1,000,000,000		1,900,000,000
Uncommitted Master Repurchase Agreements
Mortgage note and other loan payable
Number of instruments | debt_instrument		2
Uncommitted Master Repurchase Agreement 2017
Mortgage note and other loan payable
Floating rate debt		$ 300,000,000		90,809,000
Maximum borrowing capacity		$ 300,000,000	$ 400,000,000
Initial term		1 year
Number of extension options | extension		2
Period of extension option		1 year
Revolving credit facility, net		$ 299,400,000
Uncommitted Master Repurchase Agreement 2017 | Weighted Average
Mortgage note and other loan payable
Interest rate (as a percent)		2.34%
Uncommitted Master Repurchase Agreement 2016
Mortgage note and other loan payable
Maximum borrowing capacity					$ 300,000,000
Initial term		2 years
Period of extension option		1 year
Basis point fee (as a percent)	0.25%
Threshold amount for basis point fee to be applicable (less than)	$ 150,000,000
315 West 33rd Street
Mortgage note and other loan payable
Fixed rate debt		$ 250,000,000		250,000,000
315 West 33rd Street | Weighted Average
Mortgage note and other loan payable
Interest rate (as a percent)		4.24%
919 Third Avenue
Mortgage note and other loan payable
Fixed rate debt		$ 0		500,000,000
115 Spring Street
Mortgage note and other loan payable
Floating rate debt		$ 65,550,000		$ 0
115 Spring Street | Weighted Average
Mortgage note and other loan payable
Interest rate (as a percent)		3.40%
London Interbank Offered Rate (LIBOR) | Uncommitted Master Repurchase Agreement 2016 | Minimum
Mortgage note and other loan payable
Credit facility, interest rate (as a percent)		2.25%
London Interbank Offered Rate (LIBOR) | Uncommitted Master Repurchase Agreement 2016 | Maximum
Mortgage note and other loan payable
Credit facility, interest rate (as a percent)		4.00%

Corporate Indebtedness (Details

Corporate Indebtedness (Details)	Aug. 13, 2018USD ($)	Oct. 31, 2017USD ($)	Sep. 30, 2018USD ($)extension	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)extension	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Corporate Indebtedness
Carrying value			$ 1,265,550,000		$ 1,265,550,000
Debt disclosures by scheduled maturity date
Accreted Balance			651,340,000		651,340,000		$ 901,067,000
Scheduled amortization and principal repayments
Remaining 2,018			0		0
2,019			0		0
2,020			550,000,000		550,000,000
2,021			0		0
2,022			300,000,000		300,000,000
Thereafter			415,550,000		415,550,000
Total amortization of debt and principal repayments			1,265,550,000		1,265,550,000
Interest expense
Interest expense			17,052,000	$ 34,658,000	51,729,000	$ 96,740,000
Interest capitalized			(1,594,000)	(31,000)	(3,908,000)	(533,000)
Interest income			0	0	(3,000)	(5,000)
Interest expense, net			15,458,000	$ 34,627,000	47,818,000	$ 96,202,000
Senior Unsecured Notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance			650,000,000		650,000,000
Accreted Balance			654,421,000		654,421,000		905,116,000
Deferred financing costs, net			(3,081,000)		(3,081,000)		(4,049,000)
Total			651,340,000		651,340,000		901,067,000
Term Loan B, Maturity November 21, 2024 | Term loan
Corporate Indebtedness
Maximum borrowing capacity			200,000,000		200,000,000
Term Loan A, Maturity March 31, 2023 | Term loan
Corporate Indebtedness
Maximum borrowing capacity			1,300,000,000		1,300,000,000
Revolving credit facility
Corporate Indebtedness
Revolving credit facility, net			145,000,000		145,000,000
Term loan
Corporate Indebtedness
Maximum borrowing capacity			1,500,000,000		1,500,000,000
Term loan | Line of Credit
Corporate Indebtedness
Carrying value			1,500,000,000		1,500,000,000		1,500,000,000
Scheduled amortization and principal repayments
Total amortization of debt and principal repayments			1,500,000,000		1,500,000,000		1,500,000,000
4.50% Senior Unsecured Bonds Due December 2022 | Senior Unsecured Bonds
Corporate Indebtedness
Face amount		$ 100,000,000
Redemption price, percentage		105.334%
Debt disclosures by scheduled maturity date
Coupon Rate (as a percent)		4.50%
Credit Facility 2012
Corporate Indebtedness
Letters of credit			11,800,000		11,800,000
Ability to borrow under line of credit facility			1,300,000,000		1,300,000,000
Credit Facility 2012 | Line of Credit
Corporate Indebtedness
Carrying value			136,700,000		136,700,000		30,300,000
Scheduled amortization and principal repayments
Total amortization of debt and principal repayments			136,700,000		136,700,000		30,300,000
7.75% senior unsecured notes maturing on March 15, 2020 | Senior Unsecured Notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance			250,000,000		250,000,000
Accreted Balance			$ 250,000,000		$ 250,000,000		250,000,000
Coupon Rate (as a percent)			7.75%		7.75%
Initial Term (in Years)					10 years
4.50% senior unsecured notes maturing on December 01, 2022 | Senior Unsecured Notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance			$ 300,000,000		$ 300,000,000
Accreted Balance			$ 304,421,000		$ 304,421,000		305,163,000
Coupon Rate (as a percent)			4.50%		4.50%
Initial Term (in Years)					10 years
4.27% senior unsecured notes maturing December 17, 2025 | Senior Unsecured Notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance			$ 100,000,000		$ 100,000,000
Accreted Balance			$ 100,000,000		$ 100,000,000		100,000,000
Coupon Rate (as a percent)			4.27%		4.27%
Initial Term (in Years)					10 years
Mortgage and Other Loans Payable
Scheduled Amortization
Remaining 2,018			$ 0		$ 0
2,019			0		0
2,020			0		0
2,021			0		0
2,022			0		0
Thereafter			0		0
Total amortization of debt			0		0
Principal Repayments
Remaining 2,018			0		0
2,019			0		0
2,020			300,000,000		300,000,000
2,021			0		0
2,022			0		0
Thereafter			315,550,000		315,550,000
Total principal repayments			615,550,000		615,550,000
Senior Notes
Corporate Indebtedness
Carrying value			650,000,000		650,000,000
Scheduled amortization and principal repayments
Remaining 2,018			0		0
2,019			0		0
2,020			250,000,000		250,000,000
2,021			0		0
2,022			300,000,000		300,000,000
Thereafter			100,000,000		100,000,000
Total amortization of debt and principal repayments			650,000,000		650,000,000
3.25 Percent Senior Unsecured Notes Due October 2022 | Senior Unsecured Notes
Corporate Indebtedness
Carrying value			$ 499,600,000		$ 499,600,000
Debt disclosures by scheduled maturity date
Coupon Rate (as a percent)			3.25%		3.25%
Scheduled amortization and principal repayments
Total amortization of debt and principal repayments			$ 499,600,000		$ 499,600,000
Senior Notes due 2021 | Senior Notes
Corporate Indebtedness
Interest rate added to base rate (as a percent)	0.98%
Face amount	$ 350,000,000
Senior Unsecured Notes, Due August 15, 2018 | Senior Unsecured Notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance			0		0
Accreted Balance			0		0		$ 249,953,000
Revolving credit facility | Revolving Credit Facility, Maturity March 31, 2022 | Line of Credit
Corporate Indebtedness
Maximum borrowing capacity			$ 1,500,000,000		$ 1,500,000,000
Number of extensions | extension			2		2
Term of extension					6 months
Maximum borrowing capacity, optional expansion			$ 4,500,000,000		$ 4,500,000,000
Revolving credit facility | Credit Facility 2012
Corporate Indebtedness
Maximum borrowing capacity			$ 1,200,000,000		$ 1,200,000,000

Related Party Transactions (Det

Related Party Transactions (Details) - Affiliate - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Aug. 22, 2016
Related Party Transactions
Profit participation received by related party	$ 0.9	$ 0.8	$ 2.6	$ 2.5
Alliance Building Services
Related Party Transactions
Payments made for services	2.4	2.6	7	7.1
SL Green
Related Party Transactions
Allocation of salary and other operating costs from related party	2.6	3	8.2	9.2
Insurance expense incurred	$ 1	$ 1.3	$ 3.2	$ 4.1
Notes payable, related parties					$ 23.8
Interest rate					6.00%

Preferred Units (Details)

Preferred Units (Details)	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares	Aug. 31, 2015shares	Jul. 22, 2015USD ($)
Class of Stock [Line Items]
Number of company common stock issued on conversion of Series B preferred units	6.71348
Series A Preferred Units
Class of Stock [Line Items]
Fair value of embedded derivative | $	$ 0		$ 0
Partnership Interest | Series A Preferred Units
Class of Stock [Line Items]
Number of units authorized (in shares) | shares	109,161
Dividend rate, preferred units (as a percent)	3.50%
Liquidation preference of preferred units (in usd per share) | $ / shares	$ 1,000
Number of units issued (in shares) | shares		109,161
Annual dividends on preferred units (in usd per share) | $ / shares	$ 35

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Fair Value of Financial Instruments
Purchase price and other fair value adjustments	$ 0	$ 0	$ 54,860	$ 0
Carrying Value
Fair Value of Financial Instruments
Debt and preferred equity investments, net	1,977,057		1,977,057		$ 2,114,041
Fair Value
Fair Value of Financial Instruments
Estimated fair value of debt and preferred equity investments, low end of range	2,000,000		2,000,000		2,100,000
Estimated fair value of debt and preferred equity investments, high end of range	2,200,000		2,200,000		2,300,000
Level 3 | Carrying Value
Fair Value of Financial Instruments
Fixed rate debt	904,421		904,421		1,655,116
Variable rate debt	365,550		365,550		90,809
Total	1,269,971		1,269,971		1,745,925
Level 3 | Fair Value
Fair Value of Financial Instruments
Fixed rate debt	907,337		907,337		1,715,501
Variable rate debt	382,438		382,438		92,087
Total	1,289,775		1,289,775		1,807,588
Joint Venture
Fair Value of Financial Instruments
Debt and preferred equity investments, net	$ 0		0		$ 141,716
Joint Venture | 919 Third Avenue | 919 Third Avenue
Fair Value of Financial Instruments
Purchase price and other fair value adjustments			$ 54,900

Financial Instruments_ Deriva_3

Financial Instruments: Derivatives and Hedging (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Deferred net losses from terminated hedges			$ 0	$ 1,300
Interest Rate Swap
Derivative [Line Items]
Amount of Loss Recognized in Other Comprehensive Loss (Effective Portion)	$ 0	$ 0	0	0
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	0	89	0	269
Amount of Gain Recognized into Income (Ineffective Portion)	$ 0	$ 0	$ 0	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Sep. 30, 2018USD ($)
Ticonderoga Insurance Company
Line of Credit Facility [Line Items]
FHLB, advances, amount	$ 13

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Minimum initial term of noncancellable operating leases (in years)	1 year
Non-cancellable operating leases
Remaining 2,018	$ 4,934
2,019	19,736
2,020	19,736
2,021	19,886
2,022	17,730
2,023	15,424
Thereafter	237,011
Total minimum lease payments	$ 334,457

Segment Information (Details)

Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)segment	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Segment information
Number of reportable segments | segment			2
Total revenues	$ 198,587	$ 241,908	$ 615,864	$ 726,075
Net income	73,508	64,710	272,934	138,849
Total assets	7,304,548		7,304,548		$ 8,541,508
Marketing, general and administrative	131	92	405	321
Real Estate Segment
Segment information
Total revenues	149,462	193,962	472,777	577,151
Net income	39,354	24,722	172,068	7,342
Total assets	5,204,346		5,204,346		6,182,431
Debt and Preferred Equity Segment
Segment information
Total revenues	49,125	47,946	143,087	148,924
Net income	34,154	$ 39,988	100,866	$ 131,507
Total assets	$ 2,100,202		$ 2,100,202		$ 2,359,077