Empire State Realty OP (FISK) 10-Q 6 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Entity Registrant Name	Empire State Realty OP, L.P.
Entity Central Index Key	1,553,079
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Entity Filer Category	Large Accelerated Filer
Series ES operating partnership units
Entity Common Stock, Shares Outstanding		34,009,035
Series 60 operating partnership units
Entity Common Stock, Shares Outstanding		9,081,041
Series 250 operating partnership units
Entity Common Stock, Shares Outstanding		4,447,365

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Commercial real estate properties, at cost:
Land	$ 201,196	$ 201,196
Development costs	7,978	7,951
Building and improvements	2,398,964	2,249,482
Commercial real estate properties, at cost	2,608,138	2,458,629
Less: accumulated depreciation	(631,916)	(556,546)
Commercial real estate properties, net	1,976,222	1,902,083
Cash and cash equivalents	432,105	554,371
Restricted cash	64,020	61,514
Tenant and other receivables, net of allowance of $3,504 and $3,333 in 2017 and 2016, respectively	34,661	22,542
Deferred rent receivables, net of allowance of $187 and $390 in 2017 and 2016, respectively	172,665	152,074
Prepaid expenses and other assets	39,463	53,749
Deferred costs, net	268,132	277,081
Acquired below-market ground leases, net	370,187	376,060
Goodwill	491,479	491,479
Total assets	3,848,934	3,890,953
Liabilities:
Mortgage notes payable, net	720,830	759,016
Senior unsecured notes, net	592,914	590,388
Unsecured term loan facility, net	263,546	262,927
Unsecured revolving credit facility	0	0
Accounts payable and accrued expenses	142,690	134,064
Acquired below-market leases, net	70,013	82,300
Deferred revenue and other liabilities	41,320	32,212
Tenants’ security deposits	47,395	47,183
Total liabilities	1,878,708	1,908,090
Commitments and contingencies
Capital:
Private perpetual preferred units, $16.62 per unit liquidation preference, 1,560,360 issued and outstanding in 2017 and 2016	8,004	8,004
Total capital	1,970,226	1,982,863
Total liabilities and capital	3,848,934	3,890,953
Series PR operating partnership units
Capital:
ESRT partner's capital (3,004,168 and 2,990,931 general partner operating partnership units and 156,423,280 and 152,849,546 limited partner operating partnership units outstanding in 2017 and 2016, respectively)	1,153,631	1,154,136
Limited partner operating partnership units	785,927	793,360
Series ES operating partnership units
Capital:
Limited partner operating partnership units	16,741	20,091
Series 60 operating partnership units
Capital:
Limited partner operating partnership units	3,957	4,880
Series 250 operating partnership units
Capital:
Limited partner operating partnership units	$ 1,966	$ 2,392

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Tenant and other receivables allowance	$ 3,504	$ 3,333
Deferred rent receivables allowance	$ 187	$ 390
Capital
Private perpetual preferred units, liquidation preference (in USD per share)	$ 16.62	$ 16.62
Private perpetual preferred units, issued (in shares)	1,560,360	1,560,360
Private perpetual preferred units, outstanding (in shares)	1,560,360	1,560,360
General partner operating partnership units, outstanding (in shares)	159,427,448
Limited partner operating partnership units, outstanding (in shares)	140,989,373
Series PR operating partnership units
Capital
Limited partner operating partnership units, outstanding (in shares)	93,203,688	93,075,441
Series ES operating partnership units
Capital
Limited partner operating partnership units, outstanding (in shares)	34,172,111	35,729,094
Series 60 operating partnership units
Capital
Limited partner operating partnership units, outstanding (in shares)	9,137,320	9,701,402
Series 250 operating partnership units
Capital
Limited partner operating partnership units, outstanding (in shares)	4,476,254	4,746,661
ESRT | Series PR operating partnership units
Capital
General partner operating partnership units, outstanding (in shares)	3,004,168	2,990,931
Limited partner operating partnership units, outstanding (in shares)	156,423,280	152,849,546

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues:
Rental revenue	$ 122,391	$ 115,634	$ 360,348	$ 343,155
Tenant expense reimbursement	20,346	19,176	53,889	56,350
Observatory revenue	39,306	38,093	94,212	91,112
Third-party management and other fees	345	404	1,088	1,372
Other revenue and fees	4,932	2,541	19,861	6,748
Total revenues	187,320	175,848	529,398	498,737
Operating expenses:
Property operating expenses	41,270	38,585	122,009	115,075
Ground rent expenses	2,331	2,331	6,994	6,994
General and administrative expenses	12,899	11,798	36,566	35,623
Observatory expenses	8,648	7,250	23,079	21,900
Real estate taxes	26,901	24,691	76,001	71,773
Acquisition expenses	0	0	0	98
Depreciation and amortization	38,490	37,607	119,868	115,382
Total operating expenses	130,539	122,262	384,517	366,845
Total operating income	56,781	53,586	144,881	131,892
Other expenses:
Interest expense	(16,890)	(17,939)	(52,109)	(52,758)
Loss on early extinguishment of debt	(2,157)	0	(2,157)	(552)
Loss from derivative financial instruments	0	0	(289)	0
Income before income taxes	37,734	35,647	90,326	78,582
Income tax expense	(2,245)	(2,750)	(4,333)	(4,340)
Net income	35,489	32,897	85,993	74,242
Private perpetual preferred unit distributions	(234)	(234)	(702)	(702)
Net income attributable to common unitholders	$ 35,255	$ 32,663	$ 85,291	$ 73,540
Total weighted average units:
Basic (in units)	296,389	278,739	296,389	270,388
Diluted (in units)	297,871	280,614	298,089	271,028
Earnings per unit attributable to common unitholders:
Basic earnings (in USD per unit)	$ 0.12	$ 0.12	$ 0.29	$ 0.27
Diluted earnings (in USD per unit)	0.12	0.12	0.28	0.27
Dividends per unit (in USD per unit)	$ 0.105	$ 0.105	$ 0.315	$ 0.295

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 35,489	$ 32,897	$ 85,993	$ 74,242
Other comprehensive income (loss):
Change in unrealized gain (loss) on valuation of interest rate swap agreements	(1,279)	930	(14,252)	(29,305)
Other comprehensive income (loss)	(1,279)	930	(14,252)	(29,305)
Comprehensive income (loss)	$ 34,210	$ 33,827	$ 71,741	$ 44,937

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Capital - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance		$ 1,982,863
Equity compensation		10,808
Distributions		(95,186)
Net income	$ 35,489	85,993
Unrealized gain (loss) on valuation of interest rate swap agreements	(1,279)	(14,252)
Ending balance	$ 1,970,226	$ 1,970,226
General Partner | Series PR operating partnership units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)		155,841
Beginning balance		$ 1,154,136
Conversion of operating partnership units to ESRT Partner's Capital (in units)		3,558
Conversion of operating partnership units to ESRT Partner's Capital		$ 11,069
Equity compensation (in units)		28
Equity compensation		$ 476
Distributions		(49,843)
Net income		45,375
Unrealized gain (loss) on valuation of interest rate swap agreements		$ (7,582)
Ending balance (in units)	159,427	159,427
Ending balance	$ 1,153,631	$ 1,153,631
Limited Partner | Series PR operating partnership units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)		93,075
Beginning balance		$ 793,360
Conversion of operating partnership units to ESRT Partner's Capital (in units)		(1,167)
Conversion of operating partnership units to ESRT Partner's Capital		$ (9,890)
Equity compensation (in units)		1,296
Equity compensation		$ 10,332
Distributions		(29,329)
Net income		25,758
Unrealized gain (loss) on valuation of interest rate swap agreements		$ (4,304)
Ending balance (in units)	93,204	93,204
Ending balance	$ 785,927	$ 785,927
Limited Partner | Series ES operating partnership units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)		35,728
Beginning balance		$ 20,091
Conversion of operating partnership units to ESRT Partner's Capital (in units)		(1,556)
Conversion of operating partnership units to ESRT Partner's Capital		$ (803)
Distributions		(10,929)
Net income		10,064
Unrealized gain (loss) on valuation of interest rate swap agreements		$ (1,682)
Ending balance (in units)	34,172	34,172
Ending balance	$ 16,741	$ 16,741
Limited Partner | Series 60 operating partnership units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)		9,701
Beginning balance		$ 4,880
Conversion of operating partnership units to ESRT Partner's Capital (in units)		(564)
Conversion of operating partnership units to ESRT Partner's Capital		$ (252)
Distributions		(2,944)
Net income		2,729
Unrealized gain (loss) on valuation of interest rate swap agreements		$ (456)
Ending balance (in units)	9,137	9,137
Ending balance	$ 3,957	$ 3,957
Limited Partner | Series 250 operating partnership units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)		4,747
Beginning balance		$ 2,392
Conversion of operating partnership units to ESRT Partner's Capital (in units)		(271)
Conversion of operating partnership units to ESRT Partner's Capital		$ (124)
Distributions		(1,439)
Net income		1,365
Unrealized gain (loss) on valuation of interest rate swap agreements		$ (228)
Ending balance (in units)	4,476	4,476
Ending balance	$ 1,966	$ 1,966
Private Perpetual Preferred Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)		1,560
Beginning balance		$ 8,004
Distributions		(702)
Net income		$ 702
Ending balance (in units)	1,560	1,560
Ending balance	$ 8,004	$ 8,004

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flows From Operating Activities
Net income	$ 85,993	$ 74,242
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	119,868	115,382
Amortization of non-cash items within interest expense	919	516
Amortization of acquired above- and below-market leases, net	(4,154)	(6,285)
Amortization of acquired below-market ground leases	5,873	5,873
Straight-lining of rental revenue	(20,590)	(21,495)
Equity based compensation	10,808	7,254
Settlement of derivative contracts	(6,335)	0
Loss on early extinguishment of debt	2,157	552
Increase (decrease) in cash flows due to changes in operating assets and liabilities:
Restricted cash	(703)	3,120
Tenant and other receivables	(12,119)	(788)
Deferred leasing costs	(21,660)	(18,642)
Prepaid expenses and other assets	13,672	16,775
Accounts payable and accrued expenses	(8,917)	(7,223)
Deferred revenue and other liabilities	9,108	(7,213)
Net cash provided by operating activities	173,920	162,068
Cash Flows From Investing Activities
(Increase) decrease in restricted cash for investing activities	(1,590)	558
Development costs	(27)	(450)
Additions to building and improvements	(157,579)	(120,401)
Net cash used in investing activities	(159,196)	(120,293)
Cash Flows From Financing Activities
Proceeds from mortgage notes payable	315,000	50,000
Repayment of mortgage notes payable	(344,618)	(29,220)
Proceeds from unsecured revolving credit facility and term loan	265,000	50,000
Repayments of unsecured revolving credit facility and term loan	(265,000)	(90,000)
Net proceeds from the sale of common stock	0	611,278
Deferred financing costs	(12,186)	(2,905)
Distributions	(95,186)	(83,316)
Net cash (used in) provided by financing activities	(136,990)	505,837
Net (decrease) increase in cash and cash equivalents	(122,266)	547,612
Cash and cash equivalents—beginning of period	554,371	46,685
Cash and cash equivalents—end of period	432,105	594,297
Supplemental disclosures of cash flow information:
Cash paid for interest	53,918	53,286
Cash paid for income taxes	5,004	3,495
Non-cash investing and financing activities:
Building and improvements included in accounts payable and accrued expenses	72,130	71,444
Derivative instruments at fair values included in accounts payable and accrued expenses	13,378	31,227
Conversion of limited partners' operating partnership units to ESRT partner's capital	$ 11,087	$ 19,941

Description of Business and Org

Description of Business and Organization	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Organization	Description of Business and Organization As used in these condensed consolidated financial statements, unless the context otherwise requires, “we,” “us,” "our," and the "company,” mean Empire State Realty OP, L.P. and its consolidated subsidiaries. Empire State Realty OP, L.P. (the "Operating Partnership") is the entity through which Empire State Realty Trust, Inc. (“ESRT”), a self-administered and self-managed real estate investment trust ("REIT"), conducts all of its business and owns (either directly or through subsidiaries) substantially all of its assets. We own, manage, operate, acquire and reposition office and retail properties in Manhattan and the greater New York metropolitan area. As of September 30, 2017 , our total portfolio contained 10.1 million rentable square feet of office and retail space. We owned 14 office properties (including three long-term ground leasehold interests) encompassing approximately 9.4 million rentable square feet of office space. Nine of these properties are located in the midtown Manhattan market and aggregate approximately 7.6 million rentable square feet of office space, including the Empire State Building. Our Manhattan office properties also contain an aggregate of 494,935 rentable square feet of retail space on their ground floor and/or contiguous levels. Our remaining five office properties are located in Fairfield County, Connecticut and Westchester County, New York, encompassing in the aggregate approximately 1.9 million rentable square feet. The majority of square footage for these five properties is located in densely populated metropolitan communities with immediate access to mass transportation. Additionally, we have entitled land at the Stamford Transportation Center in Stamford, Connecticut, adjacent to one of our office properties, that will support the development of an approximately 380,000 rentable square foot office building and garage, which we refer to herein as Metro Tower. As of September 30, 2017 , our portfolio included four standalone retail properties located in Manhattan and two standalone retail properties located in the city center of Westport, Connecticut, encompassing 204,450 rentable square feet in the aggregate. We were organized as a Delaware limited partnership on November 28, 2011 and operations commenced upon completion of the initial public offering of ESRT’s Class A common stock and related formation transactions on October 7, 2013. ESRT, as the sole general partner in our company, has responsibility and discretion in the management and control of our company, and our limited partners, in such capacity, have no authority to transact business for, or participate in the management activities, of our company. As of September 30, 2017 , ESRT owned approximately 53.1% of our operating partnership units.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies There have been no material changes to the summary of significant accounting policies included in the section entitled "Summary of Significant Accounting Policies" in our December 31, 2016 Annual Report on Form 10-K. Basis of Quarterly Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), for interim financial information, and with the rules and regulations of the Securities and Exchange Commission (the "SEC"). Accordingly, certain information and footnote disclosures required by GAAP for complete financial statements have been condensed or omitted in accordance with such rules and regulations. In the opinion of management, all adjustments and eliminations (including intercompany balances and transactions), consisting of normal recurring adjustments, considered necessary for the fair presentation of the financial statements have been included. The results of operations for the periods presented are not necessarily indicative of the results that may be expected for the corresponding full years. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the financial statements for the year ended December 31, 2016 contained in our Annual Report on Form 10-K. We do not consider our business to be subject to material seasonal fluctuations, except that our observatory business is subject to tourism seasonality. During the past ten years, approximately 16.0% to 18.0% of our annual observatory revenue was realized in the first quarter, 26.0% to 28.0% was realized in the second quarter, 31.0% to 33.0% was realized in the third quarter and 23.0% to 25.0% was realized in the fourth quarter. We consolidate entities in which we have a controlling financial interest. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, authority to make decisions, and contractual and substantive participating rights of the partners/members. For variable interest entities ("VIE"), we consolidate the entity if we are deemed to have a variable interest in the entity and through that interest we are deemed the primary beneficiary. The primary beneficiary of a VIE 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. The primary beneficiary is required to consolidate the VIE. We had no VIEs as of September 30, 2017 and December 31, 2016. We will assess the accounting treatment for each investment we may have in the future. This assessment will include a review of each entity’s organizational agreement to determine which party has what rights and whether those rights are protective or participating. For all VIEs, we will review such agreements in order to determine which party has the power to direct the activities that most significantly impact the entity’s economic performance and benefit. In situations where we or our partner could approve, among other things, the annual budget, or leases that cover more than a nominal amount of space relative to the total rentable space at each property, we would not consolidate the investment as we consider these to be substantive participation rights that result in shared power of the activities that would most significantly impact the performance and benefit of such joint venture investment. A non-controlling interest in a consolidated subsidiary is defined as the portion of the equity (net assets) in a subsidiary not attributable, directly or indirectly, to a parent. Non-controlling interests are required to be presented as a separate component of equity in the condensed consolidated balance sheets and in the condensed consolidated statements of income by requiring earnings and other comprehensive income to be attributed to controlling and non-controlling interests. Accounting Estimates The preparation of the condensed consolidated financial statements in accordance with GAAP requires management to use estimates and assumptions that in certain circumstances affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the reported revenues and expenses. Significant items subject to such estimates and assumptions include allocation of the purchase price of acquired real estate properties among tangible and intangible assets, determination of the useful life of real estate properties and other long-lived assets, valuation and impairment analysis of commercial real estate properties and other long-lived assets, estimate of tenant expense reimbursements, valuation of the allowance for doubtful accounts, and valuation of derivative instruments, senior unsecured notes, mortgage notes payable, unsecured term loan and revolving credit facilities, and equity based compensation. These estimates are prepared using management’s best judgment, after considering past, current, and expected events and economic conditions. Actual results could differ from those estimates. Reclassification Certain prior year balances have been reclassified to conform to our current year presentation. The prior year balance of interest expense has been reclassified to separately present loss on early extinguishment of debt. Recently Issued or Adopted Accounting Standards During August 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which amends its hedge accounting model to enable entities to better portray their risk management activities in the financial statements. The amendments expand an entity’s ability to hedge nonfinancial and financial risk components and reduce complexity in fair value hedges of interest rate risk. ASU No. 2017-12 eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. It also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. ASU No. 2017-12 will be effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period. All transition requirements and elections should be applied to hedging relationships existing on the date of adoption. The effect of adoption should be reflected as of the beginning of the fiscal year of adoption (that is, the initial application date). During the quarter, we early adopted ASU No. 2017-02 using a modified retrospective approach for existing and active hedging relationships as of adoption date. The adoption of ASU No. 2017-02 did not have a material impact on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which contain amendments that modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. An entity no longer will determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Because these amendments eliminate Step 2 from the goodwill impairment test, they should reduce the cost and complexity of evaluating goodwill for impairment. ASU No. 2017-04 should be applied on a prospective basis and the amendments adopted for the annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which contain amendments to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in ASU No. 2017-01 provide a screen to determine when an integrated set of assets and activities (collectively referred to as a “set”) is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. This screen reduces the number of transactions that need to be further evaluated. Real estate acquisitions that do not meet the definition of a business will be accounted for as asset acquisitions and the corresponding acquisition costs will be capitalized rather than expensed. These amendments narrow the definition of the term output so that the term is consistent with how outputs are described in Topic 606, Revenue from Contracts with Customers. ASU No. 2017-01 will be effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The amendments should be applied prospectively on or after the effective date. No disclosures are required at transition. We believe that future acquisitions of real estate properties will be considered asset acquisitions. During November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which contain amendments that require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU No. 2016-18 will be effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. The amendments should be applied using a retrospective transition method to each period presented. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU No. 2016-15 will be effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Earlier adoption is permitted including adoption in an interim period. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which contains amendments that replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Earlier adoption as of the fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, is permitted. The amendments must be adopted through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective (that is, a modified retrospective approach). We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires that a lessee recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. ASU No. 2016-02 leaves the accounting for leases by lessors largely unchanged from previous GAAP. ASU No. 2016-02 will be effective for fiscal years beginning after December 15, 2018 and subsequent interim periods. The new standard must be adopted using a modified retrospective transition, and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. This ASU is expected to result in the recognition of a right-to-use asset and related liability to account for our future obligations under our ground lease agreements for which we are the lessee. As of September 30, 2017 , the remaining contractual payments under our ground lease agreements aggregated $61.7 million . In addition, under ASU 2016-02, lessors may only capitalize incremental direct leasing costs. As a result, we expect that we will no longer capitalize our internal leasing costs and instead will expense these costs as incurred. These costs totaled $2.3 million for the year ended December 31, 2016. We continue to evaluate the impact of adopting this new accounting standard on our consolidated financial statements. During May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which will replace all current GAAP guidance related to revenue recognition and eliminate all industry-specific guidance. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. ASU No. 2014-09 was amended in August 2015 by ASU No. 2015-14 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which defers the effective date of ASU No. 2014-09 for all entities by one year. Public business entities, certain not-for-profit entities, and certain employee benefit plans should apply the guidance in ASU No. 2014-09 to annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Earlier application is permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. ASU No. 2014-09 was further amended in December 2016 by ASU No. 2016-20 Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers which contain amendments that are intended to clarify or correct unintended application of the guidance. Those items generally are not expected to have a significant effect on current accounting practice or create a significant administrative cost for most entities. The effective date and transition requirements for the amendments are the same as the effective date and transition requirements for Topic 606. We plan to adopt this standard on the required effective date of January 1, 2018 using the modified retrospective approach and we do not expect the adoption to have a material impact on our consolidated financial statements. This standard excludes from its scope, accounting for leases which is covered by ASU No. 2016-02, Leases. However, the non-lease service components within a lease such as common area maintenance reimbursed by tenants will be considered individual performance obligations and be subject to the new revenue recognition standard, and such revenue will be recognized over the period in which the related services are performed. We expect to apply the new revenue guidance to non-lease components within tenant leases upon our adoption of the lease standard effective January 1, 2019.

Deferred Costs, Acquired Lease

Deferred Costs, Acquired Lease Intangibles and Goodwill	9 Months Ended
	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Acquired Lease Intangibles and Goodwill	Deferred Costs, Acquired Lease Intangibles and Goodwill Deferred costs, net, consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Leasing costs $ 158,780 $ 140,325 Acquired in-place lease value and deferred leasing costs 244,829 253,113 Acquired above-market leases 70,290 74,770 473,899 468,208 Less: accumulated amortization (214,466 ) (195,617 ) Total deferred costs, net, excluding net deferred financing costs $ 259,433 $ 272,591 At September 30, 2017 and December 31, 2016, $8.7 million and $4.5 million , respectively, of net deferred financing costs associated with the unsecured revolving credit facility was included in deferred costs, net on the condensed consolidated balance sheet. Amortization expense related to deferred leasing costs and acquired deferred leasing costs was $5.8 million and $6.1 million for the three months ended September 30, 2017 and 2016, respectively, and $17.9 million and $17.6 million for the nine months ended September 30, 2017 and 2016, respectively. Amortization expense related to acquired lease intangibles was $4.0 million and $5.0 million for the three months ended September 30, 2017 and 2016, respectively, and $13.0 million and $19.7 million for the nine months ended September 30, 2017 and 2016, respectively. Amortizing acquired intangible assets and liabilities consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Acquired below-market ground leases $ 396,916 $ 396,916 Less: accumulated amortization (26,729 ) (20,856 ) Acquired below-market ground leases, net $ 370,187 $ 376,060 September 30, 2017 December 31, 2016 Acquired below-market leases $ (132,723 ) $ (135,026 ) Less: accumulated amortization 62,710 52,726 Acquired below-market leases, net $ (70,013 ) $ (82,300 ) Rental revenue related to the amortization of below-market leases, net of above-market leases, was $1.6 million and $1.2 million for the three months ended September 30, 2017 and 2016, respectively, and $4.1 million and $6.3 million for the nine months ended September 30, 2017 and 2016, respectively. As of September 30, 2017 , we had goodwill of $491.5 million . Goodwill was allocated $227.5 million to the observatory reportable segment and $264.0 million to the real estate segment.

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt Debt consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): Principal Balance As of September 30, 2017 September 30, 2017 December 31, 2016 Stated Effective (1) Maturity (2) Mortgage debt collateralized by: Fixed rate mortgage debt 1333 Broadway $ 66,872 $ 67,656 6.32 % 3.73 % 1/5/2018 1400 Broadway (first lien mortgage loan) 66,909 67,714 6.12 % 3.37 % 2/5/2018 (second lien mortgage loan) 9,226 9,389 3.35 % 3.36 % 2/5/2018 111 West 33rd Street (first lien mortgage loan) 74,356 75,261 6.01 % 3.32 % 4/5/2018 (second lien mortgage loan) 9,405 9,509 6.56 % 3.62 % 4/5/2018 1350 Broadway 37,302 37,764 5.87 % 3.71 % 4/5/2018 Metro Center 94,464 95,985 3.59 % 3.66 % 11/5/2024 10 Union Square 50,000 50,000 3.70 % 3.97 % 4/1/2026 1542 Third Avenue 30,000 17,795 4.29 % 4.68 % 5/1/2027 First Stamford Place (3) 180,000 235,067 4.28 % 4.67 % 7/1/2027 1010 Third Avenue and 77 West 55th Street 39,885 26,502 4.01 % 4.45 % 1/5/2028 10 Bank Street 34,802 31,544 4.23 % 4.54 % 6/1/2032 383 Main Avenue 30,000 28,654 4.44 % 4.77 % 6/30/2032 Total mortgage debt 723,221 752,840 Senior unsecured notes - exchangeable 250,000 250,000 2.63 % 3.93 % 8/15/2019 Senior unsecured notes: (6) Series A 100,000 100,000 3.93 % 4.00 % 3/27/2025 Series B 125,000 125,000 4.09 % 4.17 % 3/27/2027 Series C 125,000 125,000 4.18 % 4.26 % 3/27/2030 Unsecured revolving credit facility (6) — — (4) (4) 8/29/2021 Unsecured term loan facility (6) 265,000 265,000 (5) (5) 8/29/2022 Total principal 1,588,221 1,617,840 Unamortized premiums, net of unamortized discount (2,301 ) 905 Deferred financing costs, net (8,630 ) (6,414 ) Total $ 1,577,290 $ 1,612,331 ______________ (1) The effective rate is the yield as of September 30, 2017 , including the effects of debt issuance costs and the amortization of the fair value of debt adjustment. (2) Pre-payment is generally allowed for each loan upon payment of a customary pre-payment penalty. (3) Represents a $164 million mortgage loan bearing interest of 4.09% and a $16 million loan bearing interest at 6.25% . (4) At September 30, 2017 , the unsecured revolving credit facility bears a floating rate at 30 day LIBOR plus 1.10% . The rate at September 30, 2017 was 2.33% . (5) The unsecured term loan facility bears a floating rate at 30 day LIBOR plus 1.20% . Pursuant to a forward interest rate swap agreement, the LIBOR rate is fixed at 2.1485% for the period beginning on August 31, 2017 through maturity. The rate at September 30, 2017 was 3.35% . (6) At September 30, 2017 , we were in compliance with all debt covenants. Mortgage Debt During April 2017, we refinanced a mortgage loan collateralized by 1542 Third Avenue. The new $30.0 million loan bears interest at a fixed rate of 4.29% and matures in May 2027. During May 2017, we refinanced a mortgage loan collateralized by 10 Bank Street. The new $35.0 million loan bears interest at a fixed rate of 4.23% and matures in June 2032. During June 2017, we refinanced a mortgage loan collateralized by First Stamford Place. The new $180.0 million loans bear a blended interest rate of 4.28% and mature in July 2027. One mortgage loan is for $164.0 million and bears an interest rate of 4.09% . The second loan is for $16.0 million and bears an interest rate of 6.25% . During June 2017, we refinanced a mortgage loan collateralized by 1010 Third Avenue and 77 West 55th Street. The new $40.0 million loan bears interest at a fixed rate of 4.01% and matures in January 2028. During June 2017, we refinanced a mortgage loan collateralized by 383 Main Avenue. The new $30.0 million loan bears interest at a fixed rate of 4.44% and matures in June 2032. Principal Payments Aggregate required principal payments at September 30, 2017 are as follows (amounts in thousands): Year Amortization Maturities Total 2017 $ 1,983 $ — $ 1,983 2018 4,417 262,210 266,627 2019 3,790 250,000 253,790 2020 3,938 — 3,938 2021 4,090 — 4,090 Thereafter 43,407 1,014,386 1,057,793 Total $ 61,625 $ 1,526,596 $ 1,588,221 Deferred Financing Costs Deferred financing costs, net, consisted of the following at September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Financing costs $ 23,333 $ 23,145 Less: accumulated amortization (6,004 ) (12,241 ) Total deferred financing costs, net $ 17,329 $ 10,904 At September 30, 2017 and December 31, 2016, $8.7 million and $4.5 million , respectively, of net deferred financing costs associated with the unsecured revolving credit facility was included in deferred costs, net on the condensed consolidated balance sheet. Amortization expense related to deferred financing costs was $1.0 million and $1.3 million for the three months ended September 30, 2017 and 2016, respectively, and $3.6 million and $3.7 million for the nine months ended September 30, 2017 and 2016, respectively, and was included in interest expense. Unsecured Revolving Credit and Term Loan Facility During August 2017, we entered into an amended and restated senior unsecured revolving credit and term loan facility (the “Facility”) with Bank of America, N.A., as administrative agent, Merrill Lynch, Pierce, Fenner & Smith Incorporated and Wells Fargo Securities, LLC as Joint Lead Arrangers and Joint Bookrunners, Wells Fargo, National Association and Capital One, National Association, as co-syndication agents, and the lenders party thereto. The Facility amended and restated the credit facility dated as of January 23, 2015, with Bank of America, N.A., Merrill Lynch, Goldman Sachs and the other lenders party thereto. In connection with the modification of the credit facility and term loan, we incurred a loss on early extinguishment of debt of $2.2 million which is reflected in our condensed consolidated statement of income for the nine months ended September 30, 2017. This transaction extended the unsecured revolving credit facility maturity, lowered borrowing costs and added flexibility to the financial covenants. The Facility is in the original principal amount of up to $1.365 billion , which consists of a $1.1 billion revolving credit facility and a $265 million term loan facility. The new revolving credit facility replaced a credit facility which was due to mature in January 2019 and was undrawn as of September 30, 2017. The term loan facility was borrowed in full at closing and used to repay a $265 million term loan that had been due in 2022. We may request the Facility be increased through one or more increases in the revolving credit facility or one or more increases in the term loan facility or the addition of new pari passu term loan tranches, for a maximum aggregate principal amount not to exceed $1.75 billion . The initial maturity of the unsecured revolving credit facility is August 2021. We have the option to extend the initial term for up to two additional 6 -month periods, subject to certain conditions, including the payment of an extension fee equal to 0.0625% and 0.075% of the then outstanding commitments under the unsecured revolving credit facility on the first and the second extensions, respectively. T he term loan facility matures on August 2022. We may prepay the loans under the Facility at any time, subject to reimbursement of the lenders’ breakage and redeployment costs in the case of prepayment of Eurodollar Rate borrowings. Exchangeable Senior Notes Issued in August 2014, the $250.0 million 2.625% Exchangeable Senior Notes (“ 2.625% Exchangeable Senior Notes”) are due August 15, 2019. The 2.625% Exchangeable Senior Notes will be exchangeable into cash, shares of Class A common stock or a combination of cash and shares of Class A common stock, at our election. We have asserted that it is our intent and ability to settle the principal amount of the 2.625% Exchangeable Senior Notes in cash. As of September 30, 2017 , the exchange rate of the 2.625% Exchangeable Senior Notes was 51.7101 shares per $1,000 principal amount of notes (equivalent to an initial exchange price of approximately $19.34 per share of Class A common stock), subject to adjustment, as described in the related indenture governing the 2.625% Exchangeable Senior Notes. For the three and nine months ended September 30, 2017 , total interest expense related to the 2.625% Exchangeable Senior Notes was $2.4 million and $7.3 million , respectively, consisting of (i) the contractual interest expense of $1.6 million and $4.9 million , respectively, (ii) the additional non-cash interest expense of $0.7 million and $2.0 million , respectively, relating to the accretion of the debt discount, and (iii) the amortization of deferred financing costs of $0.1 million and $0.4 million , respectively. For the three and nine months ended September 30, 2016 , total interest expense related to the 2.625% Exchangeable Senior Notes was $2.4 million and $7.3 million , respectively, consisting of (i) the contractual interest expense of $1.6 million and $4.9 million , respectively, (ii) the additional non-cash interest expense of $0.7 million and $2.0 million , respectively, relating to the accretion of the debt discount, and (iii) the amortization of deferred financing costs of $0.1 million and $0.4 million , respectively.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	9 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Accounts payable and accrued expenses $ 106,420 $ 102,866 Payable to the estate of Leona M. Helmsley (1) 18,367 18,367 Interest rate swap agreements liability 13,378 5,591 Accrued interest payable 3,903 6,230 Due to affiliated companies 622 1,010 Accounts payable and accrued expenses $ 142,690 $ 134,064 ___________ (1) Reflects a payable to the estate of Leona M. Helmsley, as required under our formation agreements, for New York City transfer taxes which would have been payable in absence of the estate's exemption from such tax. The taxing authority's final approval of such exemption was issued during the three months ended September 30, 2017, and upon receipt of the confirming documents we made this payment to the estate of Leona M. Helmsley on October 2, 2017.

Financial Instruments and Fair

Financial Instruments and Fair Values	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Values	Financial Instruments and Fair Values Derivative Financial Instruments We use derivative financial instruments primarily to manage interest rate risk and such derivatives are not considered speculative. These derivative instruments are typically in the form of interest rate swap and forward agreements and the primary objective is to minimize interest rate risks associated with investing and financing activities. The counterparties of these arrangements are major financial institutions with which we may also have other financial relationships. We are exposed to credit risk in the event of non-performance by these counterparties; however, we currently do not anticipate that any of the counterparties will fail to meet their obligations. We have agreements with our derivative counterparties that contain a provision where if we either default or are capable of being declared in default on any of our indebtedness, then we could also be declared in default on our derivative obligations. As of September 30, 2017 , the fair value of derivatives in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $13.4 million . If we had breached any of these provisions at September 30, 2017 , we could have been required to settle our obligations under the agreements at their termination value of $13.4 million . As of September 30, 2017 , we had interest rate LIBOR swaps with an aggregate notional value of $790.0 million . The notional value does not represent exposure to credit, interest rate or market risks. As of September 30, 2017 , the fair value of these derivative instruments amounted to ( $13.4 million ) which is included in accounts payable and accrued expenses on the condensed consolidated balance sheet. As of December 31, 2016, the fair value of these derivative instruments amounted to $0.6 million which was included in prepaid expenses and other assets and ( $5.6 million ) which was included in accounts payable and accrued expenses on the condensed consolidated balance sheet. These interest rate swaps have been designated as cash flow hedges and hedge the future cash outflows on our mortgage debt and also on our term loan facility that is subject to a floating interest rate. As of September 30, 2017 and 2016, these cash flow hedges are deemed highly effective and a net unrealized gain (loss) of $(1.6) million and $0.9 million for the three months ended September 30, 2017 and 2016, respectively, and a net unrealized gain (loss) of $(14.7) million and $(29.3) million for the nine months ended September 30, 2017 and 2016, respectively, are reflected in the condensed consolidated statements of comprehensive income (loss). Amounts reported in accumulated other comprehensive income (loss) related to derivatives will be reclassified to interest expense as interest payments are made on the debt. We estimate that $2.9 million of the current balance held in accumulated other comprehensive income (loss) will be reclassified into interest expense within the next 12 months relating to the interest rate swap contracts in effect as of September 30, 2017 . The table below summarizes the terms of agreements and the fair values of our derivative financial instruments as of September 30, 2017 and December 31, 2016 (dollar amounts in thousands): September 30, 2017 December 31, 2016 Derivative Notional Amount Receive Rate Pay Rate Effective Date Expiration Date Asset Liability Asset Liability Interest rate swap $ 265,000 1 Month LIBOR 2.1485% August 31, 2017 August 24, 2022 $ — $ (3,436 ) $ — $ (1,634 ) Interest rate swap (1) 100,000 3 Month LIBOR 2.5050% July 5, 2017 July 5, 2027 — — — (684 ) Interest rate swap (1) (2) 80,000 3 Month LIBOR 2.5050% July 5, 2017 July 5, 2027 — — — (685 ) Interest rate swap 100,000 3 Month LIBOR 2.4860% January 5, 2018 January 5, 2028 — (1,448 ) 224 — Interest rate swap 100,000 3 Month LIBOR 2.4860% January 5, 2018 January 5, 2028 — (1,448 ) 223 — Interest rate swap 75,000 3 Month LIBOR 2.4860% January 5, 2018 January 5, 2028 — (1,086 ) 167 — Interest rate swap 75,000 3 Month LIBOR 2.7620% June 1, 2018 June 1, 2028 — (2,592 ) — (1,295 ) Interest rate swap 75,000 3 Month LIBOR 2.7620% June 1, 2018 June 1, 2028 — (2,591 ) — (1,293 ) Interest rate swap 100,000 3 Month LIBOR 2.4625% June 1, 2018 June 1, 2028 — (777 ) — — $ — $ (13,378 ) $ 614 $ (5,591 ) (1) During June 2017, these swaps aggregating $180.0 million were terminated in connection with the refinancing of several of our mortgage debt (see Note 4 Debt). As of September 30, 2017, the deferred net losses from these terminated hedges amounted to $5.9 million which is included in accumulated other comprehensive loss relating to net unrealized loss from derivative financial instruments. (2) During March 2017, $20.0 million of an original notional amount of $100.0 million was terminated. In connection with the partial termination and re-designation of the related cash flow hedges, $0.3 million is recognized as a loss from derivative financial instruments and included in Other Expenses on the condensed consolidated statement of income for the nine months ended September 30, 2017. There was no loss from derivative financial instruments for the three months ended September 30, 2017 and for the three and nine months ended September 30, 2016. The table below shows the effect of our derivative financial instruments designated as cash flow hedges on accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2017 and 2016 (amounts in thousands): Three Months Ended Nine Months Ended Effects of Cash Flow Hedges September 30, 2017 September 30, 2016 September 30, 2017 September 30, 2016 Amount of gain (loss) recognized in other comprehensive income (loss) $ (1,638 ) $ 930 $ (14,654 ) $ (29,305 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (359 ) — (402 ) — The table below shows the effect of our derivative financial instruments designated as cash flow hedges on the condensed consolidated income statements for the three and nine months ended September 30, 2017 and 2016 (amounts in thousands): Three Months Ended Nine Months Ended Effects of Cash Flow Hedges September 30, 2017 September 30, 2016 September 30, 2017 September 30, 2016 Total interest (expense) presented in the condensed consolidated income statements in which the effects of cash flow hedges are recorded $ (16,890 ) $ (17,939 ) $ (52,109 ) $ (52,758 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (359 ) — (402 ) — Fair Valuation The estimated fair values at September 30, 2017 and December 31, 2016 were determined by management, using available market information and appropriate valuation methodologies. Considerable judgment is necessary to interpret market data and develop estimated fair value. Accordingly, the estimates presented herein are not necessarily indicative of the amounts we could realize on disposition of the financial instruments. The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The fair value of our senior unsecured notes - Exchangeable was derived from quoted prices in active markets and is classified as Level 2 since trading volumes are low. The fair value of derivative instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Although the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by ourselves and our counterparties. The impact of such credit valuation adjustments, determined based on the fair value of each individual contract, was not significant to the overall valuation. As a result, all of our derivatives were classified as Level 2 of the fair value hierarchy. The fair value of our mortgage notes payable, senior unsecured notes - Series A, B and C, and unsecured term loan facility which are determined using Level 3 inputs, are estimated by discounting the future cash flows using current interest rates at which similar borrowings could be made to us. The following tables summarize the carrying and estimated fair values of our financial instruments as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 Estimated Fair Value Carrying Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ — $ — $ — $ — $ — Interest rate swaps included in accounts payable and accrued expenses 13,378 13,378 — 13,378 — Mortgage notes payable 720,830 712,365 — — 712,365 Senior unsecured notes - Exchangeable 243,923 281,068 — 281,068 — Senior unsecured notes - Series A, B, and C 348,991 344,267 — — 344,267 Unsecured term loan facility 263,546 265,000 — — 265,000 December 31, 2016 Estimated Fair Value Carrying Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ 614 $ 614 $ — $ 614 $ — Interest rate swaps included in accounts payable and accrued expenses 5,591 5,591 — 5,591 — Mortgage notes payable 759,016 755,640 — — 755,640 Senior unsecured notes - Exchangeable 241,474 282,435 — 282,435 — Senior unsecured notes - Series A, B, and C 348,914 339,274 — — 339,274 Unsecured term loan facility 262,927 265,000 — — 265,000 Disclosure about the fair value of financial instruments is based on pertinent information available to us as of September 30, 2017 and December 31, 2016. 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.

Rental Income

Rental Income	9 Months Ended
	Sep. 30, 2017
Leases [Abstract]
Rental Income	Rental Income We lease various office spaces to tenants over terms ranging from one to 16 years. Certain leases have renewal options for additional terms. The leases provide for base monthly rentals and reimbursements for real estate taxes, escalations linked to the consumer price index or common area maintenance known as operating expense escalation. Operating expense reimbursements are reflected in our condensed consolidated statements of income as tenant expense reimbursement.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings Except as described below, as of September 30, 2017 , we were not involved in any material litigation, nor, to our knowledge, was any material litigation threatened against us or our properties, other than routine litigation arising in the ordinary course of business such as disputes with tenants. We believe that the costs and related liabilities, if any, which may result from such actions will not materially affect our condensed consolidated financial position, operating results or liquidity. As previously disclosed, on or about October 14, 2014, 12 former investors in Empire State Building Associates L.L.C. (“ESBA”), which prior to the initial public offering of our company, (the "Offering"), owned the fee title to the Empire State Building, filed an arbitration with the American Arbitration Association against Peter L. Malkin, Anthony E. Malkin, Thomas N. Keltner, Jr., and our subsidiary ESRT MH Holdings LLC, the former supervisor of ESBA, as respondents. The statement of claim alleges breach of fiduciary duty and related claims in connection with the Offering and formation transactions. These investors had opted out of a prior class action brought regarding the Offering and formation transactions that was settled with court approval. The statement of claim in the arbitration seeks monetary damages and declaratory relief. The respondents filed an answering statement and counterclaims. On December 18, 2014, these claimants also filed a complaint in the United States District Court for the Southern District of New York alleging the same claims that they asserted in the arbitration. As alleged in the complaint, the claimants filed this lawsuit to toll the statute of limitations on their claims in the event it is determined that the claims are not subject to arbitration, and they planned to move to stay the lawsuit in favor of the pending arbitration. On February 2, 2015, the claimants filed an amended complaint adding an additional claim and making other non-substantive modifications to the original complaint. On March 12, 2015, the court stayed the action on consent of all parties pending the arbitration. The arbitration hearings commenced in May 2016 and have proceeded for a select number of hearing sessions since that time. Additional hearing sessions are scheduled to resume in November and December 2017. The respondents believe the allegations in the arbitration are entirely without merit, and they intend to defend them vigorously. In connection with the Offering and formation transactions, we entered into indemnification agreements with our directors, executive officers and chairman emeritus, providing for the indemnification by us for certain liabilities and expenses incurred as a result of actions brought, or threatened to be brought, against them. As a result, Anthony E. Malkin, Peter L. Malkin and Thomas N. Keltner, Jr. have defense and indemnity rights from us with respect to the above-referenced arbitration. Unfunded Capital Expenditures At September 30, 2017 , we estimate that we will incur approximately $78.2 million of capital expenditures (including tenant improvements and leasing commissions) on our properties pursuant to existing lease agreements. We expect to fund these capital expenditures with operating cash flow, additional property level mortgage financings, our unsecured credit facility, cash on hand and other borrowings. Future property acquisitions may require substantial capital investments for refurbishment and leasing costs. We expect that these financing requirements will be met in a similar fashion. Ground Leases Aggregate requir ed payments on ground leases at September 30, 2017 were as follows (amounts in thousands): 2017 $ 380 2018 1,518 2019 1,518 2020 1,518 2021 1,518 Thereafter 55,212 $ 61,664 Concentration of Credit Risk Financial instruments that subject us to credit risk consist primarily of cash and cash equivalents, restricted cash, tenant and other receivables and deferred rent receivables. At September 30, 2017 , we held on deposit at various major financial institutions cash and cash equivalents and restricted cash balances in excess of amounts insured by the Federal Deposit Insurance Corporation. Asset Retirement Obligations We are required to accrue costs that we are legally obligated to incur on retirement of our properties which result from acquisition, construction, development and/or normal operation of such properties. Retirement includes sale, abandonment or disposal of a property. Under that standard, a conditional asset retirement obligation represents a legal obligation to perform an asset retirement activity in which the timing and/or method of settlement is conditional on a future event that may or may not be within a company’s control and a liability for a conditional asset retirement obligation must be recorded if the fair value of the obligation can be reasonably estimated. Environmental site assessments and investigations have identified asbestos or asbestos-containing building materials in certain of our properties. As of September 30, 2017 , management has no plans to remove or alter these properties in a manner that would trigger federal and other applicable regulations for asbestos removal, and accordingly, the obligations to remove the asbestos or asbestos-containing building materials from these properties have indeterminable settlement dates. As such, we are unable to reasonably estimate the fair value of the associated conditional asset retirement obligation. However, ongoing asbestos abatement, maintenance programs and other required documentation are carried out as required and related costs are expensed as incurred. Other Environmental Matters Certain of our properties have been inspected for soil contamination due to pollutants, which may have occurred prior to our ownership of these properties or subsequently in connection with its development and/or its use. Required remediation to such properties has been completed, and as of September 30, 2017 , management believes that there are no obligations related to environmental remediation other than maintaining the affected sites in conformity with the relevant authority’s mandates and filing the required documents. All such maintenance costs are expensed as incurred. We expect that resolution of the environmental matters relating to the above will not have a material impact on our business, assets, consolidated financial condition, results of operations or liquidity. However, we cannot be certain that we have identified all environmental liabilities at our properties, that all necessary remediation actions have been or will be undertaken at our properties or that we will be indemnified, in full or at all, in the event that such environmental liabilities arise. Insurance Coverage We carry insurance coverage on our properties of types and in amounts with deductibles that we believe are in line with coverage customarily obtained by owners of similar properties.

Capital

Capital	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note Disclosure, Disclosure of Compensation Related Costs, Share-based Payments and Earnings Per Share [Abstract]
Capital	Capital During 2016, Q REIT Holding LLC, a Qatar Financial Centre limited liability company and a wholly owned subsidiary of the Qatar Investment Authority, a governmental authority of the State of Qatar (“QREIT”, together with any eligible transferee, “QIA”) purchased 29,610,854 newly issued ESRT Class A common shares at $21.00 per share, resulting in gross proceeds of $621.8 million . The proceeds were contributed to us and we issued 29,610,854 Series PR units to ESRT. At August 23, 2016, the 29,610,854 units were equivalent to a 9.9% economic interest in us. QIA has a top-up right to acquire a pro rata number of additional shares from ESRT if ESRT should issue new shares to third parties. In connection with the share issuance to QIA, ESRT agreed, subject to certain minimum thresholds and conditions, to indemnify QIA for certain applicable U.S. federal and state taxes paid by QIA in connection with any dividends ESRT pays that are attributable to capital gains from the sale or exchange of any U.S. real property interests. If ESRT were to trigger its tax indemnification obligations under this agreement, we and ESRT would be required to pay QIA for the resulting tax consequences, as applicable. As of September 30, 2017 , there were 300,416,821 operating partnership units outstanding, of which 159,427,448 , or 53.1% , were owned by ESRT and 140,989,373 , or 46.9% , were owned by other partners, including ESRT directors, members of senior management and other employees. Long-term incentive plan ("LTIP") units are a special class of partnership interests. Each LTIP unit awarded will be deemed equivalent to an award of one share of ESRT stock under the First Amended and Restated Empire State Realty Trust, Inc. and Empire State Realty OP, L.P. 2013 Equity Incentive Plan ("2013 Plan"), reducing the availability for other equity awards on a one-for-one basis. The vesting period for LTIP units, if any, will be determined at the time of issuance. Under the terms of the LTIP units, we will revalue for tax purposes its assets upon the occurrence of certain specified events, and any increase in valuation from the time of grant until such event will be allocated first to the holders of LTIP units to equalize the capital accounts of such holders with the capital accounts of unitholders. Subject to any agreed upon exceptions, once vested and having achieved parity with unitholders, LTIP units are convertible into Series PR operating partnership units on a one-for-one basis. With the exception of performance based LTIP units granted in 2016 and 2017, all LTIP units issued in connection with annual equity awards, whether vested or not, receive the same per unit distributions as operating partnership units, which equal per share dividends (both regular and special) on our common stock. Performance based LTIP units granted in 2016 and 2017 receive 10% of such distributions currently, unless and until such LTIP units are earned based on performance, at which time they will receive the accrued and unpaid 90% and will commence receiving 100% of such distributions thereafter. Distributions Total distributions paid to OP unitholders were $31.5 million and $94.5 million for the three and nine months ended September 30, 2017 , respectively, and $31.4 million and $82.6 million for the three and nine months ended September 30, 2016, respectively. Total distributions paid to preferred unitholders were $0.2 million and $0.7 million for the three and nine months ended September 30, 2017 , respectively, and $0.2 million and $0.7 million for the three and nine months ended September 30, 2016, respectively. Incentive and Share-Based Compensation The 2013 Plan provides for grants to directors, employees and consultants consisting of stock options, restricted stock, dividend equivalents, stock payments, performance shares, LTIP units, stock appreciation rights and other incentive awards. An aggregate of 12.2 million shares of ESRT common stock is authorized for issuance under awards granted pursuant to the 2013 Plan, and as of September 30, 2017 , 7.0 million shares of ESRT common stock remain available for future issuance. In March 2017, we made grants of LTIP units to executive officers under the 2013 Plan. At such time, we granted to executive officers a total of 313,275 LTIP units that are subject to time-based vesting and 865,742 LTIP units that are subject to performance-based vesting, with fair market values of $6.1 million for the time-based vesting awards and $9.6 million for the performance-based vesting awards. In March 2017, we made grants of LTIP units and restricted stock to certain other employees under the 2013 Plan. At such time, we granted to certain other employees a total of 47,993 LTIP units and 34,407 shares of restricted stock that are subject to time-based vesting and 95,156 LTIP units that are subject to performance-based vesting, with fair market values of $1.6 million for the time-based vesting awards and $1.0 million for the performance-based vesting awards. The awards subject to time-based vesting vest ratably over four years from January 1, 2017, subject generally to the grantee's continued employment. The first installment vests on January 1, 2018 and the remainder will vest thereafter in three equal annual installments. The vesting of the LTIP units subject to performance-based vesting is based on the achievement of absolute and relative total stockholder return hurdles over a three -year performance period, commencing on January 1, 2017. Following the completion of the three -year performance period, our compensation committee will determine the number of LTIP units to which the grantee is entitled based on our performance relative to the performance hurdles set forth in the LTIP unit award agreements the grantee entered into in connection with the award grant. These units then vest in two installments, with the first installment vesting on January 1, 2020 and the second installment vesting on January 1, 2021, subject generally to the grantee's continued employment on those dates. In May 2017, we made grants of LTIP units to our non-employee directors under the 2013 Plan. At such time, we granted a total of 50,408 LTIP units that are subject to time-based vesting with fair market values of $1.0 million . The awards vest ratably over three years from the date of the grant, subject generally to the director's continued service on our Board of Directors. In February 2016, we made grants of LTIP units to executive officers under the 2013 Plan. At such time, we granted to executive officers a total of 368,225 LTIP units that are subject to time-based vesting and 1,230,228 LTIP units that are subject to performance-based vesting, with fair market values of $5.6 million for the time-based vesting awards and $8.8 million for the performance-based vesting awards. In February 2016, we made grants of LTIP units and restricted stock to certain other employees under the 2013 Plan. At such time, we granted to certain other employees a total of 47,168 LTIP units and 44,198 shares of restricted stock that are subject to time-based vesting and 112,925 LTIP units that are subject to performance-based vesting, with fair market values of $1.4 million for the time-based vesting awards and $0.8 million for the performance-based vesting awards. The awards subject to time-based vesting vest ratably over four years from January 1, 2016, subject generally to the grantee's continued employment. The first installment vested on January 1, 2017 and the remainder will vest thereafter in three equal annual installments. The vesting of the LTIP units subject to performance-based vesting is based on the achievement of absolute and relative total stockholder return hurdles over a three -year performance period, commencing on January 1, 2016. Following the completion of the three -year performance period, our compensation committee will determine the number of LTIP units to which the grantee is entitled based on our performance relative to the performance hurdles set forth in the LTIP unit award agreements the grantee entered into in connection with the award grant. These units then vest in two installments, with the first installment vesting on January 1, 2019 and the second installment vesting on January 1, 2020, subject generally to the grantee's continued employment on those dates. In February 2016, we made a grant of LTIP units to an executive officer under the 2013 Plan. We granted a total of 62,814 LTIP units with a fair market value of $1.0 million . The award is subject to time-based vesting of 30% after three years, 30% after four years, and 40% after five years, subject to the grantee's continued employment. In June 2016, we made grants of LTIP units to our non-employee directors under the 2013 Plan. At such time, we granted a total of 43,257 LTIP units that are subject to time-based vesting with fair market values of $0.8 million . The awards vest ratably over three years from the date of the grant, subject generally to the director's continued service on our Board of Directors. We made other grants during 2016 under the 2013 Plan with fair market values of $0.1 million in the aggregate. Share-based compensation is measured at the fair value of the award on the date of grant and recognized as an expense on a straight-line basis over the vesting period. For the performance-based LTIP units and restricted stock awards, the fair value of the awards was estimated using a Monte Carlo Simulation model. Our stock price, along with the prices of the comparative indexes, is assumed to follow the Geometric Brownian Motion Process. Geometric Brownian Motion is a common assumption when modeling in financial markets, as it allows the modeled quantity (in this case the stock price) to vary randomly from its current value and take any value greater than zero. The volatilities of the returns on our stock price and the comparative indexes were estimated based on implied volatilities and historical volatilities using a six -year look-back period. The expected growth rate of the stock prices over the performance period is determined with consideration of the risk free rate as of the grant date. For LTIP unit awards that are time-based, the fair value of the awards was estimated based on the fair value of our stock at the grant date discounted for the restriction period during which the LTIP units cannot be redeemed or transferred and the uncertainty regarding if, and when, the book capital account of the LTIP units will equal that of the common units. For restricted stock awards that are time-based, we estimate the stock compensation expense based on the fair value of the stock at the grant date. LTIP units and ESRT restricted stock issued during the nine months ended September 30, 2017 and 2016 were valued at $19.4 million and $18.4 million , respectively. The weighted-average per unit or share fair value was $13.77 and $9.60 for grants issued in 2017 and 2016, respectively. The per unit or share granted in 2017 was estimated on the respective dates of grant using the following assumptions: an expected life of 2.8 years, a dividend rate of 2.05% , a risk-free interest rate of 1.55% , and an expected price volatility of 20.0% . The per unit or share granted in 2016 was estimated on the respective dates of grant using the following assumptions: an expected life of 2.8 years , a dividend rate of 2.10% , a risk-free interest rate of 0.84% and an expected price volatility of 24.0% . No other stock options, dividend equivalents, or stock appreciation rights were issued or outstanding in 2017. The following is a summary of ESRT restricted stock and LTIP unit activity for the nine months ended September 30, 2017 : Restricted Stock LTIP Units Weighted Average Grant Fair Value Unvested balance at December 31, 2016 107,793 2,881,629 $ 10.01 Vested (17,923 ) (323,982 ) 13.74 Granted 34,407 1,372,574 13.77 Forfeited or unearned (2,509 ) (77,227 ) 5.36 Unvested balance at September 30, 2017 121,768 3,852,994 $ 11.11 The LTIP unit and ESRT restricted stock awards will immediately vest upon the later of (i) the date the grantee attains the age of 60 and (ii) the date on which grantee has first completed ten years of continuous service with our company or its affiliates. For award agreements that qualify, we recognize noncash compensation expense on the grant date for the time-based awards and ratably over the vesting period for the performance-based awards, and accordingly, we recognized $0.2 million and $0.9 million for the three and nine months ended September 30, 2017 , respectively, and $0.1 million and $0.6 million for the three and nine months ended September 30, 2016, respectively. Unrecognized compensation expense was $0.9 million at September 30, 2017 , which will be recognized over a weighted average period of 2.4 years. For the remainder of the LTIP unit and ESRT restricted stock awards, we recognize noncash compensation expense ratably over the vesting period, and accordingly, we recognized noncash compensation expense of $3.7 million and $9.9 million for the three and nine months ended September 30, 2017 , respectively, and $2.5 million and $6.7 million for the three and nine months ended September 30, 2016, respectively. Unrecognized compensation expense was $26.5 million at September 30, 2017 , which will be recognized over a weighted average period of 2.5 years. Earnings Per Unit Earnings per unit for the three and nine months ended September 30, 2017 and 2016 is computed as follows (amounts in thousands, except per share amounts): Three Months Ended, Nine Months Ended, September 30, 2017 September 30, 2016 September 30, 2017 September 30, 2016 Numerator: Net income $ 35,489 $ 32,897 $ 85,993 $ 74,242 Private perpetual preferred unit distributions (234 ) (234 ) (702 ) (702 ) Earnings allocated to unvested units (228 ) (225 ) (582 ) (575 ) Net income attributable to common unitholders - basic and diluted $ 35,027 $ 32,438 $ 84,709 $ 72,965 Denominator: Weighted average units outstanding - basic 296,389 278,739 296,389 270,388 Effect of dilutive securities: Stock-based compensation plans 762 1,090 848 378 Exchangeable senior notes 720 785 852 262 Weighted average units outstanding - diluted 297,871 280,614 298,089 271,028 Earnings per share: Basic 0.12 0.12 0.29 0.27 Diluted $ 0.12 $ 0.12 $ 0.28 $ 0.27 There were 954,533 and 840,092 antidilutive units for the three and nine months ended September 30, 2017 , respectively, and 1,033,044 and 757,119 antidilutive units for the three and nine months ended September 30, 2016, respectively.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Supervisory Fee Revenue We earned supervisory fees from entities affiliated with Anthony E. Malkin, our Chairman and Chief Executive Officer, of $0.3 million and $0.3 million for the three months ended September 30, 2017 and 2016, respectively, and $0.9 million and $1.1 million for the nine months ended September 30, 2017 and 2016, respectively. These fees are included within third-party management and other fees. Property Management Fee Revenue We earned property management fees from entities affiliated with Anthony E. Malkin of $0.1 million and $0.1 million for the three months ended September 30, 2017 and 2016, respectively, and $0.2 million and $0.3 million for the nine months ended September 30, 2017 and 2016, respectively. These fees are included within third-party management and other fees. Other We were reimbursed at allocable cost for 647 square feet of shared office space, equipment, and administrative support, as was done prior to our formation, and we received rent generally at market rental rate for 3,074 square feet of leased space, from entities affiliated with Anthony E. Malkin, at one of our properties aggregating $0.07 million and $0.2 million for the three and nine months ended September 30, 2016, respectively. During August 2016, such entities moved from the previously shared office and leased spaces to relocate to a new 5,351 square foot leased space at one of our properties, paying rent generally at a market rental rate. Under such new lease, the tenant has the right to cancel such lease without special payment on 90 days’ notice. We now have a shared use agreement with such tenant, to occupy a portion of the leased premises as the office location for Peter L. Malkin, our chairman emeritus and employee, utilizing approximately 15% of the space, for which we pay an allocable pro rata share of the cost to such tenant. We also have agreements with these entities to provide them with general computer-related support. Total revenue aggregated $0.1 million and $0.3 million for the three and nine months ended September 30, 2017, respectively. One of ESRT's directors, James D. Robinson IV, is a general partner in an investment fund, which owns more than a 10% economic and voting interest in one of our tenants, OnDeck Capital, with an annualized rent of $5.8 million and $5.7 million as of September 30, 2017 and 2016, respectively.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting We have identified two reportable segments: (1) real estate and (2) observatory. Our real estate segment includes all activities related to the ownership, management, operation, acquisition, redevelopment, repositioning and disposition of our real estate assets. Our observatory segment includes the operation of the 86th and 102nd floor observatories at the Empire State Building. These two lines of businesses are managed separately because each business requires different support infrastructures, provides different services and has dissimilar economic characteristics such as investments needed, stream of revenues and marketing strategies. We account for intersegment sales and rent as if the sales or rent were to third parties, that is, at current market prices. The following tables provide components of segment profit for each segment for the three and nine months ended September 30, 2017 and 2016 (amounts in thousands): Three Months Ended September 30, 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 122,391 $ — $ — $ 122,391 Intercompany rental revenue 23,301 — (23,301 ) — Tenant expense reimbursement 20,346 — — 20,346 Observatory revenue — 39,306 — 39,306 Third-party management and other fees 345 — — 345 Other revenue and fees 4,932 — — 4,932 Total revenues 171,315 39,306 (23,301 ) 187,320 Operating expenses: Property operating expenses 41,270 — — 41,270 Intercompany rent expense — 23,301 (23,301 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 12,899 — — 12,899 Observatory expenses — 8,648 — 8,648 Real estate taxes 26,901 — — 26,901 Depreciation and amortization 38,473 17 — 38,490 Total operating expenses 121,874 31,966 (23,301 ) 130,539 Total operating income 49,441 7,340 — 56,781 Other expenses: Interest expense (16,890 ) — — (16,890 ) Loss on early extinguishment of debt (2,157 ) — — (2,157 ) Loss from derivative financial instruments — — — — Income before income taxes 30,394 7,340 — 37,734 Income tax expense (264 ) (1,981 ) — (2,245 ) Net income $ 30,130 $ 5,359 $ — $ 35,489 Segment assets $ 3,582,935 $ 265,999 $ — $ 3,848,934 Expenditures for segment assets $ 40,320 $ 13,411 $ — $ 53,731 Three Months Ended September 30, 2016 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 115,634 $ — $ — $ 115,634 Intercompany rental revenue 22,983 — (22,983 ) — Tenant expense reimbursement 19,176 — — 19,176 Observatory revenue — 38,093 — 38,093 Third-party management and other fees 404 — — 404 Other revenue and fees 2,536 5 — 2,541 Total revenues 160,733 38,098 (22,983 ) 175,848 Operating expenses: Property operating expenses 38,585 — — 38,585 Intercompany rent expense — 22,983 (22,983 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 11,798 — — 11,798 Observatory expenses — 7,250 — 7,250 Real estate taxes 24,691 — — 24,691 Acquisition expenses — — — — Depreciation and amortization 37,421 186 — 37,607 Total operating expenses 114,826 30,419 (22,983 ) 122,262 Total operating income 45,907 7,679 — 53,586 Other expenses: Interest expense (17,939 ) — — (17,939 ) Loss on early extinguishment of debt — — — — Loss from derivative financial instruments — — — — Income before income taxes 27,968 7,679 — 35,647 Income tax expense (332 ) (2,418 ) — (2,750 ) Net income $ 27,636 $ 5,261 $ — $ 32,897 Segment assets $ 3,636,262 $ 246,307 $ — $ 3,882,569 Expenditures for segment assets $ 52,828 $ — $ — $ 52,828 Nine Months Ended September 30, 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 360,348 $ — $ — $ 360,348 Intercompany rental revenue 57,354 — (57,354 ) — Tenant expense reimbursement 53,889 — — 53,889 Observatory revenue — 94,212 — 94,212 Third-party management and other fees 1,088 — — 1,088 Other revenue and fees 19,861 — — 19,861 Total revenues 492,540 94,212 (57,354 ) 529,398 Operating expenses: Property operating expenses 122,009 — — 122,009 Intercompany rent expense — 57,354 (57,354 ) — Ground rent expense 6,994 — — 6,994 General and administrative expenses 36,566 — — 36,566 Observatory expenses — 23,079 — 23,079 Real estate taxes 76,001 — — 76,001 Acquisition expenses — — — — Depreciation and amortization 119,764 104 — 119,868 Total operating expenses 361,334 80,537 (57,354 ) 384,517 Total operating income 131,206 13,675 — 144,881 Other expenses: Interest expense (52,109 ) — — (52,109 ) Loss on early extinguishment of debt (2,157 ) — — (2,157 ) Loss from derivative financial instruments (289 ) — — (289 ) Income before income taxes 76,651 13,675 — 90,326 Income tax expense (960 ) (3,373 ) — (4,333 ) Net income $ 75,691 $ 10,302 $ — $ 85,993 Expenditures for segment assets $ 142,854 $ 20,261 $ — $ 163,115 Nine Months Ended September 30, 2016 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 343,155 $ — $ — $ 343,155 Intercompany rental revenue 55,189 — (55,189 ) — Tenant expense reimbursement 56,350 — — 56,350 Observatory revenue — 91,112 — 91,112 Third-party management and other fees 1,372 — — 1,372 Other revenue and fees 6,738 10 — 6,748 Total revenues 462,804 91,122 (55,189 ) 498,737 Operating expenses: Property operating expenses 115,075 — — 115,075 Intercompany rent expense — 55,189 (55,189 ) — Ground rent expense 6,994 — — 6,994 General and administrative expenses 35,623 — — 35,623 Observatory expenses — 21,900 — 21,900 Real estate taxes 71,773 — — 71,773 Acquisition expenses 98 — — 98 Depreciation and amortization 115,002 380 — 115,382 Total operating expenses 344,565 77,469 (55,189 ) 366,845 Total operating income 118,239 13,653 — 131,892 Other expenses: Interest expense (52,758 ) — — (52,758 ) Loss on early extinguishment of debt (552 ) — — (552 ) Loss from derivative financial instruments — — — — Income before income taxes 64,929 13,653 — 78,582 Income tax expense (1,018 ) (3,322 ) — (4,340 ) Net income $ 63,911 $ 10,331 $ — $ 74,242 Expenditures for segment assets $ 140,052 $ 47 $ — $ 140,099

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events None.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Quarterly Presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), for interim financial information, and with the rules and regulations of the Securities and Exchange Commission (the "SEC"). Accordingly, certain information and footnote disclosures required by GAAP for complete financial statements have been condensed or omitted in accordance with such rules and regulations. In the opinion of management, all adjustments and eliminations (including intercompany balances and transactions), consisting of normal recurring adjustments, considered necessary for the fair presentation of the financial statements have been included.
Principles of Consolidation	The results of operations for the periods presented are not necessarily indicative of the results that may be expected for the corresponding full years. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the financial statements for the year ended December 31, 2016 contained in our Annual Report on Form 10-K. We do not consider our business to be subject to material seasonal fluctuations, except that our observatory business is subject to tourism seasonality.
Principles of Consolidation for Variable Interest Entities	We consolidate entities in which we have a controlling financial interest. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, authority to make decisions, and contractual and substantive participating rights of the partners/members. For variable interest entities ("VIE"), we consolidate the entity if we are deemed to have a variable interest in the entity and through that interest we are deemed the primary beneficiary. The primary beneficiary of a VIE 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. The primary beneficiary is required to consolidate the VIE. We had no VIEs as of September 30, 2017 and December 31, 2016. We will assess the accounting treatment for each investment we may have in the future. This assessment will include a review of each entity’s organizational agreement to determine which party has what rights and whether those rights are protective or participating. For all VIEs, we will review such agreements in order to determine which party has the power to direct the activities that most significantly impact the entity’s economic performance and benefit. In situations where we or our partner could approve, among other things, the annual budget, or leases that cover more than a nominal amount of space relative to the total rentable space at each property, we would not consolidate the investment as we consider these to be substantive participation rights that result in shared power of the activities that would most significantly impact the performance and benefit of such joint venture investment. A non-controlling interest in a consolidated subsidiary is defined as the portion of the equity (net assets) in a subsidiary not attributable, directly or indirectly, to a parent. Non-controlling interests are required to be presented as a separate component of equity in the condensed consolidated balance sheets and in the condensed consolidated statements of income by requiring earnings and other comprehensive income to be attributed to controlling and non-controlling interests.
Accounting Estimates	The preparation of the condensed consolidated financial statements in accordance with GAAP requires management to use estimates and assumptions that in certain circumstances affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the reported revenues and expenses. Significant items subject to such estimates and assumptions include allocation of the purchase price of acquired real estate properties among tangible and intangible assets, determination of the useful life of real estate properties and other long-lived assets, valuation and impairment analysis of commercial real estate properties and other long-lived assets, estimate of tenant expense reimbursements, valuation of the allowance for doubtful accounts, and valuation of derivative instruments, senior unsecured notes, mortgage notes payable, unsecured term loan and revolving credit facilities, and equity based compensation. These estimates are prepared using management’s best judgment, after considering past, current, and expected events and economic conditions. Actual results could differ from those estimates.
Reclassification	Certain prior year balances have been reclassified to conform to our current year presentation. The prior year balance of interest expense has been reclassified to separately present loss on early extinguishment of debt.
Recently Issued or Adopted Accounting Standards	During August 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which amends its hedge accounting model to enable entities to better portray their risk management activities in the financial statements. The amendments expand an entity’s ability to hedge nonfinancial and financial risk components and reduce complexity in fair value hedges of interest rate risk. ASU No. 2017-12 eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. It also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. ASU No. 2017-12 will be effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period. All transition requirements and elections should be applied to hedging relationships existing on the date of adoption. The effect of adoption should be reflected as of the beginning of the fiscal year of adoption (that is, the initial application date). During the quarter, we early adopted ASU No. 2017-02 using a modified retrospective approach for existing and active hedging relationships as of adoption date. The adoption of ASU No. 2017-02 did not have a material impact on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which contain amendments that modify the concept of impairment from the condition that exists when the carrying amount of goodwill exceeds its implied fair value to the condition that exists when the carrying amount of a reporting unit exceeds its fair value. An entity no longer will determine goodwill impairment by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Because these amendments eliminate Step 2 from the goodwill impairment test, they should reduce the cost and complexity of evaluating goodwill for impairment. ASU No. 2017-04 should be applied on a prospective basis and the amendments adopted for the annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which contain amendments to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in ASU No. 2017-01 provide a screen to determine when an integrated set of assets and activities (collectively referred to as a “set”) is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. This screen reduces the number of transactions that need to be further evaluated. Real estate acquisitions that do not meet the definition of a business will be accounted for as asset acquisitions and the corresponding acquisition costs will be capitalized rather than expensed. These amendments narrow the definition of the term output so that the term is consistent with how outputs are described in Topic 606, Revenue from Contracts with Customers. ASU No. 2017-01 will be effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The amendments should be applied prospectively on or after the effective date. No disclosures are required at transition. We believe that future acquisitions of real estate properties will be considered asset acquisitions. During November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which contain amendments that require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU No. 2016-18 will be effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. The amendments should be applied using a retrospective transition method to each period presented. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU No. 2016-15 will be effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Earlier adoption is permitted including adoption in an interim period. We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which contains amendments that replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Earlier adoption as of the fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, is permitted. The amendments must be adopted through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective (that is, a modified retrospective approach). We are evaluating the impact of adopting this new accounting standard on our consolidated financial statements. During February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires that a lessee recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. ASU No. 2016-02 leaves the accounting for leases by lessors largely unchanged from previous GAAP. ASU No. 2016-02 will be effective for fiscal years beginning after December 15, 2018 and subsequent interim periods. The new standard must be adopted using a modified retrospective transition, and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. This ASU is expected to result in the recognition of a right-to-use asset and related liability to account for our future obligations under our ground lease agreements for which we are the lessee. As of September 30, 2017 , the remaining contractual payments under our ground lease agreements aggregated $61.7 million . In addition, under ASU 2016-02, lessors may only capitalize incremental direct leasing costs. As a result, we expect that we will no longer capitalize our internal leasing costs and instead will expense these costs as incurred. These costs totaled $2.3 million for the year ended December 31, 2016. We continue to evaluate the impact of adopting this new accounting standard on our consolidated financial statements. During May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which will replace all current GAAP guidance related to revenue recognition and eliminate all industry-specific guidance. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. ASU No. 2014-09 was amended in August 2015 by ASU No. 2015-14 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which defers the effective date of ASU No. 2014-09 for all entities by one year. Public business entities, certain not-for-profit entities, and certain employee benefit plans should apply the guidance in ASU No. 2014-09 to annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Earlier application is permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. ASU No. 2014-09 was further amended in December 2016 by ASU No. 2016-20 Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers which contain amendments that are intended to clarify or correct unintended application of the guidance. Those items generally are not expected to have a significant effect on current accounting practice or create a significant administrative cost for most entities. The effective date and transition requirements for the amendments are the same as the effective date and transition requirements for Topic 606. We plan to adopt this standard on the required effective date of January 1, 2018 using the modified retrospective approach and we do not expect the adoption to have a material impact on our consolidated financial statements. This standard excludes from its scope, accounting for leases which is covered by ASU No. 2016-02, Leases. However, the non-lease service components within a lease such as common area maintenance reimbursed by tenants will be considered individual performance obligations and be subject to the new revenue recognition standard, and such revenue will be recognized over the period in which the related services are performed. We expect to apply the new revenue guidance to non-lease components within tenant leases upon our adoption of the lease standard effective January 1, 2019.

Deferred Costs, Acquired Leas21

Deferred Costs, Acquired Lease Intangibles and Goodwill (Tables)	9 Months Ended
	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Net	Deferred costs, net, consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Leasing costs $ 158,780 $ 140,325 Acquired in-place lease value and deferred leasing costs 244,829 253,113 Acquired above-market leases 70,290 74,770 473,899 468,208 Less: accumulated amortization (214,466 ) (195,617 ) Total deferred costs, net, excluding net deferred financing costs $ 259,433 $ 272,591 Deferred financing costs, net, consisted of the following at September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Financing costs $ 23,333 $ 23,145 Less: accumulated amortization (6,004 ) (12,241 ) Total deferred financing costs, net $ 17,329 $ 10,904
Amortizing Acquired Intangible Assets and Liabilities	Amortizing acquired intangible assets and liabilities consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Acquired below-market ground leases $ 396,916 $ 396,916 Less: accumulated amortization (26,729 ) (20,856 ) Acquired below-market ground leases, net $ 370,187 $ 376,060 September 30, 2017 December 31, 2016 Acquired below-market leases $ (132,723 ) $ (135,026 ) Less: accumulated amortization 62,710 52,726 Acquired below-market leases, net $ (70,013 ) $ (82,300 )

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Long-Term Debt	Debt consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): Principal Balance As of September 30, 2017 September 30, 2017 December 31, 2016 Stated Effective (1) Maturity (2) Mortgage debt collateralized by: Fixed rate mortgage debt 1333 Broadway $ 66,872 $ 67,656 6.32 % 3.73 % 1/5/2018 1400 Broadway (first lien mortgage loan) 66,909 67,714 6.12 % 3.37 % 2/5/2018 (second lien mortgage loan) 9,226 9,389 3.35 % 3.36 % 2/5/2018 111 West 33rd Street (first lien mortgage loan) 74,356 75,261 6.01 % 3.32 % 4/5/2018 (second lien mortgage loan) 9,405 9,509 6.56 % 3.62 % 4/5/2018 1350 Broadway 37,302 37,764 5.87 % 3.71 % 4/5/2018 Metro Center 94,464 95,985 3.59 % 3.66 % 11/5/2024 10 Union Square 50,000 50,000 3.70 % 3.97 % 4/1/2026 1542 Third Avenue 30,000 17,795 4.29 % 4.68 % 5/1/2027 First Stamford Place (3) 180,000 235,067 4.28 % 4.67 % 7/1/2027 1010 Third Avenue and 77 West 55th Street 39,885 26,502 4.01 % 4.45 % 1/5/2028 10 Bank Street 34,802 31,544 4.23 % 4.54 % 6/1/2032 383 Main Avenue 30,000 28,654 4.44 % 4.77 % 6/30/2032 Total mortgage debt 723,221 752,840 Senior unsecured notes - exchangeable 250,000 250,000 2.63 % 3.93 % 8/15/2019 Senior unsecured notes: (6) Series A 100,000 100,000 3.93 % 4.00 % 3/27/2025 Series B 125,000 125,000 4.09 % 4.17 % 3/27/2027 Series C 125,000 125,000 4.18 % 4.26 % 3/27/2030 Unsecured revolving credit facility (6) — — (4) (4) 8/29/2021 Unsecured term loan facility (6) 265,000 265,000 (5) (5) 8/29/2022 Total principal 1,588,221 1,617,840 Unamortized premiums, net of unamortized discount (2,301 ) 905 Deferred financing costs, net (8,630 ) (6,414 ) Total $ 1,577,290 $ 1,612,331 ______________ (1) The effective rate is the yield as of September 30, 2017 , including the effects of debt issuance costs and the amortization of the fair value of debt adjustment. (2) Pre-payment is generally allowed for each loan upon payment of a customary pre-payment penalty. (3) Represents a $164 million mortgage loan bearing interest of 4.09% and a $16 million loan bearing interest at 6.25% . (4) At September 30, 2017 , the unsecured revolving credit facility bears a floating rate at 30 day LIBOR plus 1.10% . The rate at September 30, 2017 was 2.33% . (5) The unsecured term loan facility bears a floating rate at 30 day LIBOR plus 1.20% . Pursuant to a forward interest rate swap agreement, the LIBOR rate is fixed at 2.1485% for the period beginning on August 31, 2017 through maturity. The rate at September 30, 2017 was 3.35% . (6) At September 30, 2017 , we were in compliance with all debt covenants.
Aggregate Required Principal Payments	Aggregate required principal payments at September 30, 2017 are as follows (amounts in thousands): Year Amortization Maturities Total 2017 $ 1,983 $ — $ 1,983 2018 4,417 262,210 266,627 2019 3,790 250,000 253,790 2020 3,938 — 3,938 2021 4,090 — 4,090 Thereafter 43,407 1,014,386 1,057,793 Total $ 61,625 $ 1,526,596 $ 1,588,221
Deferred Costs, Net	Deferred costs, net, consisted of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Leasing costs $ 158,780 $ 140,325 Acquired in-place lease value and deferred leasing costs 244,829 253,113 Acquired above-market leases 70,290 74,770 473,899 468,208 Less: accumulated amortization (214,466 ) (195,617 ) Total deferred costs, net, excluding net deferred financing costs $ 259,433 $ 272,591 Deferred financing costs, net, consisted of the following at September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Financing costs $ 23,333 $ 23,145 Less: accumulated amortization (6,004 ) (12,241 ) Total deferred financing costs, net $ 17,329 $ 10,904

Accounts Payable and Accrued 23

Accounts Payable and Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 December 31, 2016 Accounts payable and accrued expenses $ 106,420 $ 102,866 Payable to the estate of Leona M. Helmsley (1) 18,367 18,367 Interest rate swap agreements liability 13,378 5,591 Accrued interest payable 3,903 6,230 Due to affiliated companies 622 1,010 Accounts payable and accrued expenses $ 142,690 $ 134,064 ___________ (1) Reflects a payable to the estate of Leona M. Helmsley, as required under our formation agreements, for New York City transfer taxes which would have been payable in absence of the estate's exemption from such tax. The taxing authority's final approval of such exemption was issued during the three months ended September 30, 2017, and upon receipt of the confirming documents we made this payment to the estate of Leona M. Helmsley on October 2, 2017.

Financial Instruments and Fai24

Financial Instruments and Fair Values (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Summary of the Terms of Agreements and the Fair Value of Derivative Financial Instruments	The table below summarizes the terms of agreements and the fair values of our derivative financial instruments as of September 30, 2017 and December 31, 2016 (dollar amounts in thousands): September 30, 2017 December 31, 2016 Derivative Notional Amount Receive Rate Pay Rate Effective Date Expiration Date Asset Liability Asset Liability Interest rate swap $ 265,000 1 Month LIBOR 2.1485% August 31, 2017 August 24, 2022 $ — $ (3,436 ) $ — $ (1,634 ) Interest rate swap (1) 100,000 3 Month LIBOR 2.5050% July 5, 2017 July 5, 2027 — — — (684 ) Interest rate swap (1) (2) 80,000 3 Month LIBOR 2.5050% July 5, 2017 July 5, 2027 — — — (685 ) Interest rate swap 100,000 3 Month LIBOR 2.4860% January 5, 2018 January 5, 2028 — (1,448 ) 224 — Interest rate swap 100,000 3 Month LIBOR 2.4860% January 5, 2018 January 5, 2028 — (1,448 ) 223 — Interest rate swap 75,000 3 Month LIBOR 2.4860% January 5, 2018 January 5, 2028 — (1,086 ) 167 — Interest rate swap 75,000 3 Month LIBOR 2.7620% June 1, 2018 June 1, 2028 — (2,592 ) — (1,295 ) Interest rate swap 75,000 3 Month LIBOR 2.7620% June 1, 2018 June 1, 2028 — (2,591 ) — (1,293 ) Interest rate swap 100,000 3 Month LIBOR 2.4625% June 1, 2018 June 1, 2028 — (777 ) — — $ — $ (13,378 ) $ 614 $ (5,591 ) (1) During June 2017, these swaps aggregating $180.0 million were terminated in connection with the refinancing of several of our mortgage debt (see Note 4 Debt). As of September 30, 2017, the deferred net losses from these terminated hedges amounted to $5.9 million which is included in accumulated other comprehensive loss relating to net unrealized loss from derivative financial instruments. (2) During March 2017, $20.0 million of an original notional amount of $100.0 million was terminated. In connection with the partial termination and re-designation of the related cash flow hedges, $0.3 million is recognized as a loss from derivative financial instruments and included in Other Expenses on the condensed consolidated statement of income for the nine months ended September 30, 2017. There was no loss from derivative financial instruments for the three months ended September 30, 2017 and for the three and nine months ended September 30, 2016.
Effect of Derivative Financial Instruments Designated as Cash Flow Hedges	The table below shows the effect of our derivative financial instruments designated as cash flow hedges on accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2017 and 2016 (amounts in thousands): Three Months Ended Nine Months Ended Effects of Cash Flow Hedges September 30, 2017 September 30, 2016 September 30, 2017 September 30, 2016 Amount of gain (loss) recognized in other comprehensive income (loss) $ (1,638 ) $ 930 $ (14,654 ) $ (29,305 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (359 ) — (402 ) — The table below shows the effect of our derivative financial instruments designated as cash flow hedges on the condensed consolidated income statements for the three and nine months ended September 30, 2017 and 2016 (amounts in thousands): Three Months Ended Nine Months Ended Effects of Cash Flow Hedges September 30, 2017 September 30, 2016 September 30, 2017 September 30, 2016 Total interest (expense) presented in the condensed consolidated income statements in which the effects of cash flow hedges are recorded $ (16,890 ) $ (17,939 ) $ (52,109 ) $ (52,758 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (359 ) — (402 ) —
Summary of the Carrying and Estimated Fair Values of Financial Instruments	The following tables summarize the carrying and estimated fair values of our financial instruments as of September 30, 2017 and December 31, 2016 (amounts in thousands): September 30, 2017 Estimated Fair Value Carrying Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ — $ — $ — $ — $ — Interest rate swaps included in accounts payable and accrued expenses 13,378 13,378 — 13,378 — Mortgage notes payable 720,830 712,365 — — 712,365 Senior unsecured notes - Exchangeable 243,923 281,068 — 281,068 — Senior unsecured notes - Series A, B, and C 348,991 344,267 — — 344,267 Unsecured term loan facility 263,546 265,000 — — 265,000 December 31, 2016 Estimated Fair Value Carrying Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ 614 $ 614 $ — $ 614 $ — Interest rate swaps included in accounts payable and accrued expenses 5,591 5,591 — 5,591 — Mortgage notes payable 759,016 755,640 — — 755,640 Senior unsecured notes - Exchangeable 241,474 282,435 — 282,435 — Senior unsecured notes - Series A, B, and C 348,914 339,274 — — 339,274 Unsecured term loan facility 262,927 265,000 — — 265,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Aggregate Required Payments on Ground Leases	Aggregate requir ed payments on ground leases at September 30, 2017 were as follows (amounts in thousands): 2017 $ 380 2018 1,518 2019 1,518 2020 1,518 2021 1,518 Thereafter 55,212 $ 61,664

Capital (Tables)

Capital (Tables)	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note Disclosure, Disclosure of Compensation Related Costs, Share-based Payments and Earnings Per Share [Abstract]
Summary of ERST Restricted Stock and LTIP Unit	The following is a summary of ESRT restricted stock and LTIP unit activity for the nine months ended September 30, 2017 : Restricted Stock LTIP Units Weighted Average Grant Fair Value Unvested balance at December 31, 2016 107,793 2,881,629 $ 10.01 Vested (17,923 ) (323,982 ) 13.74 Granted 34,407 1,372,574 13.77 Forfeited or unearned (2,509 ) (77,227 ) 5.36 Unvested balance at September 30, 2017 121,768 3,852,994 $ 11.11
Earnings Per Unit	Earnings per unit for the three and nine months ended September 30, 2017 and 2016 is computed as follows (amounts in thousands, except per share amounts): Three Months Ended, Nine Months Ended, September 30, 2017 September 30, 2016 September 30, 2017 September 30, 2016 Numerator: Net income $ 35,489 $ 32,897 $ 85,993 $ 74,242 Private perpetual preferred unit distributions (234 ) (234 ) (702 ) (702 ) Earnings allocated to unvested units (228 ) (225 ) (582 ) (575 ) Net income attributable to common unitholders - basic and diluted $ 35,027 $ 32,438 $ 84,709 $ 72,965 Denominator: Weighted average units outstanding - basic 296,389 278,739 296,389 270,388 Effect of dilutive securities: Stock-based compensation plans 762 1,090 848 378 Exchangeable senior notes 720 785 852 262 Weighted average units outstanding - diluted 297,871 280,614 298,089 271,028 Earnings per share: Basic 0.12 0.12 0.29 0.27 Diluted $ 0.12 $ 0.12 $ 0.28 $ 0.27

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Components of Segment Profit for Each Segment	The following tables provide components of segment profit for each segment for the three and nine months ended September 30, 2017 and 2016 (amounts in thousands): Three Months Ended September 30, 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 122,391 $ — $ — $ 122,391 Intercompany rental revenue 23,301 — (23,301 ) — Tenant expense reimbursement 20,346 — — 20,346 Observatory revenue — 39,306 — 39,306 Third-party management and other fees 345 — — 345 Other revenue and fees 4,932 — — 4,932 Total revenues 171,315 39,306 (23,301 ) 187,320 Operating expenses: Property operating expenses 41,270 — — 41,270 Intercompany rent expense — 23,301 (23,301 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 12,899 — — 12,899 Observatory expenses — 8,648 — 8,648 Real estate taxes 26,901 — — 26,901 Depreciation and amortization 38,473 17 — 38,490 Total operating expenses 121,874 31,966 (23,301 ) 130,539 Total operating income 49,441 7,340 — 56,781 Other expenses: Interest expense (16,890 ) — — (16,890 ) Loss on early extinguishment of debt (2,157 ) — — (2,157 ) Loss from derivative financial instruments — — — — Income before income taxes 30,394 7,340 — 37,734 Income tax expense (264 ) (1,981 ) — (2,245 ) Net income $ 30,130 $ 5,359 $ — $ 35,489 Segment assets $ 3,582,935 $ 265,999 $ — $ 3,848,934 Expenditures for segment assets $ 40,320 $ 13,411 $ — $ 53,731 Three Months Ended September 30, 2016 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 115,634 $ — $ — $ 115,634 Intercompany rental revenue 22,983 — (22,983 ) — Tenant expense reimbursement 19,176 — — 19,176 Observatory revenue — 38,093 — 38,093 Third-party management and other fees 404 — — 404 Other revenue and fees 2,536 5 — 2,541 Total revenues 160,733 38,098 (22,983 ) 175,848 Operating expenses: Property operating expenses 38,585 — — 38,585 Intercompany rent expense — 22,983 (22,983 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 11,798 — — 11,798 Observatory expenses — 7,250 — 7,250 Real estate taxes 24,691 — — 24,691 Acquisition expenses — — — — Depreciation and amortization 37,421 186 — 37,607 Total operating expenses 114,826 30,419 (22,983 ) 122,262 Total operating income 45,907 7,679 — 53,586 Other expenses: Interest expense (17,939 ) — — (17,939 ) Loss on early extinguishment of debt — — — — Loss from derivative financial instruments — — — — Income before income taxes 27,968 7,679 — 35,647 Income tax expense (332 ) (2,418 ) — (2,750 ) Net income $ 27,636 $ 5,261 $ — $ 32,897 Segment assets $ 3,636,262 $ 246,307 $ — $ 3,882,569 Expenditures for segment assets $ 52,828 $ — $ — $ 52,828 Nine Months Ended September 30, 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 360,348 $ — $ — $ 360,348 Intercompany rental revenue 57,354 — (57,354 ) — Tenant expense reimbursement 53,889 — — 53,889 Observatory revenue — 94,212 — 94,212 Third-party management and other fees 1,088 — — 1,088 Other revenue and fees 19,861 — — 19,861 Total revenues 492,540 94,212 (57,354 ) 529,398 Operating expenses: Property operating expenses 122,009 — — 122,009 Intercompany rent expense — 57,354 (57,354 ) — Ground rent expense 6,994 — — 6,994 General and administrative expenses 36,566 — — 36,566 Observatory expenses — 23,079 — 23,079 Real estate taxes 76,001 — — 76,001 Acquisition expenses — — — — Depreciation and amortization 119,764 104 — 119,868 Total operating expenses 361,334 80,537 (57,354 ) 384,517 Total operating income 131,206 13,675 — 144,881 Other expenses: Interest expense (52,109 ) — — (52,109 ) Loss on early extinguishment of debt (2,157 ) — — (2,157 ) Loss from derivative financial instruments (289 ) — — (289 ) Income before income taxes 76,651 13,675 — 90,326 Income tax expense (960 ) (3,373 ) — (4,333 ) Net income $ 75,691 $ 10,302 $ — $ 85,993 Expenditures for segment assets $ 142,854 $ 20,261 $ — $ 163,115 Nine Months Ended September 30, 2016 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 343,155 $ — $ — $ 343,155 Intercompany rental revenue 55,189 — (55,189 ) — Tenant expense reimbursement 56,350 — — 56,350 Observatory revenue — 91,112 — 91,112 Third-party management and other fees 1,372 — — 1,372 Other revenue and fees 6,738 10 — 6,748 Total revenues 462,804 91,122 (55,189 ) 498,737 Operating expenses: Property operating expenses 115,075 — — 115,075 Intercompany rent expense — 55,189 (55,189 ) — Ground rent expense 6,994 — — 6,994 General and administrative expenses 35,623 — — 35,623 Observatory expenses — 21,900 — 21,900 Real estate taxes 71,773 — — 71,773 Acquisition expenses 98 — — 98 Depreciation and amortization 115,002 380 — 115,382 Total operating expenses 344,565 77,469 (55,189 ) 366,845 Total operating income 118,239 13,653 — 131,892 Other expenses: Interest expense (52,758 ) — — (52,758 ) Loss on early extinguishment of debt (552 ) — — (552 ) Loss from derivative financial instruments — — — — Income before income taxes 64,929 13,653 — 78,582 Income tax expense (1,018 ) (3,322 ) — (4,340 ) Net income $ 63,911 $ 10,331 $ — $ 74,242 Expenditures for segment assets $ 140,052 $ 47 $ — $ 140,099

Description of Business and O28

Description of Business and Organization - Narrative (Details)	9 Months Ended
	Sep. 30, 2017ft²parceloffice_and_property
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	10,100,000
OP units owned by the Company (as a percent)	53.10%
Office Building
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	9,400,000
Number of properties | office_and_property	14
Office Building | Manhattan
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	7,600,000
Number of properties | office_and_property	9
Office Building | Fairfield County, Connecticut and Westchester County, New York
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	1,900,000
Number of properties | office_and_property	5
Development Parcel
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of properties | parcel	3
Retail Site | Manhattan and Westport, Connecticut
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	204,450
Retail Site | Manhattan
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	494,935
Number of properties | office_and_property	4
Retail Site | Westport, Connecticut
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of properties | office_and_property	2
Other Property | Stamford, Connecticut
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	380,000

Summary of Significant Accoun29

Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounting Policies [Line Items]
Capitalized internal leasing costs		$ 2,300
Minimum
Accounting Policies [Line Items]
Observatory revenue realized during the first quarter, previous ten years (as a percent)	16.00%
Observatory revenue realized during the second quarter, previous ten years (as a percent)	26.00%
Observatory revenue realized during the third quarter, previous ten years (as a percent)	31.00%
Observatory revenue realized during the fourth quarter, previous ten years (as a percent)	23.00%
Maximum
Accounting Policies [Line Items]
Observatory revenue realized during the first quarter, previous ten years (as a percent)	18.00%
Observatory revenue realized during the second quarter, previous ten years (as a percent)	28.00%
Observatory revenue realized during the third quarter, previous ten years (as a percent)	33.00%
Observatory revenue realized during the fourth quarter, previous ten years (as a percent)	25.00%
Ground lease agreements
Accounting Policies [Line Items]
Remaining contractual payments under ground lease agreements	$ 61,664

Deferred Costs, Acquired Leas30

Deferred Costs, Acquired Lease Intangibles and Goodwill - Deferred Costs, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Leasing costs	$ 158,780	$ 140,325
Total deferred costs, gross amount	473,899	468,208
Less: accumulated amortization	(214,466)	(195,617)
Total deferred costs, net, excluding net deferred financing costs	259,433	272,591
Acquired in-place lease value and deferred leasing costs
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets	244,829	253,113
Acquired above-market leases
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets	$ 70,290	$ 74,770

Deferred Costs, Acquired Leas31

Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Deferred Costs [Line Items]
Amortization expense related to deferred leasing costs	$ 5,800	$ 6,100	$ 17,900	$ 17,600
Revenue related to amortization of acquired above- and below-market leases, net	1,600	1,200	4,154	6,285
Goodwill	491,479		491,479		$ 491,479
Lease agreements
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	4,000	$ 5,000	13,000	$ 19,700
Observatory
Deferred Costs [Line Items]
Goodwill	227,500		227,500
Real estate
Deferred Costs [Line Items]
Goodwill	264,000		264,000
Revolving credit facility | Unsecured revolving credit facility
Deferred Costs [Line Items]
Net deferred financing costs	$ 8,700		$ 8,700		$ 4,500

Deferred Costs, Acquired Leas32

Deferred Costs, Acquired Lease Intangibles and Goodwill - Amortizing Acquired Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Acquired below-market ground leases
Acquired below-market ground leases, gross	$ 396,916	$ 396,916
Less: accumulated amortization	(26,729)	(20,856)
Acquired below-market ground leases, net	370,187	376,060
Acquired below-market leases
Acquired below-market leases, gross	(132,723)	(135,026)
Less: accumulated amortization	62,710	52,726
Acquired below-market leases, net	$ (70,013)	$ (82,300)

Debt - Long-Term Debt (Details)

Debt - Long-Term Debt (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Aug. 31, 2017	Jun. 30, 2017	May 31, 2017	Apr. 30, 2017	Dec. 31, 2016	Aug. 31, 2014
Debt Instrument [Line Items]
Unsecured facility	$ 0					$ 0
Deferred financing costs, net	(17,329,000)					(10,904,000)
Total	720,830,000					759,016,000
Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	723,221,000					752,840,000
Total principal	1,588,221,000					1,617,840,000
Unamortized premiums, net of unamortized discount	(2,301,000)					905,000
Deferred financing costs, net	(8,630,000)					(6,414,000)
Total	1,577,290,000					1,612,331,000
1333 Broadway | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 66,872,000					67,656,000
Stated Rate	6.32%
Effective Rate	3.73%
1400 Broadway - First Lien | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 66,909,000					67,714,000
Stated Rate	6.12%
Effective Rate	3.37%
1400 Broadway - Second Lien | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 9,226,000					9,389,000
Stated Rate	3.35%
Effective Rate	3.36%
111 West 33rd Street - First Lien | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 74,356,000					75,261,000
Stated Rate	6.01%
Effective Rate	3.32%
111 West 33rd Street - Second Lien | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 9,405,000					9,509,000
Stated Rate	6.56%
Effective Rate	3.62%
1350 Broadway | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 37,302,000					37,764,000
Stated Rate	5.87%
Effective Rate	3.71%
Metro Center | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 94,464,000					95,985,000
Stated Rate	3.59%
Effective Rate	3.66%
10 Union Square | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 50,000,000					50,000,000
Stated Rate	3.70%
Effective Rate	3.97%
1542 Third Avenue | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 30,000,000					17,795,000
Stated Rate	4.29%				4.29%
Effective Rate	4.68%
Face amount					$ 30,000,000
First Stamford Place | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 180,000,000					235,067,000
Stated Rate	4.28%		4.28%
Effective Rate	4.67%
Face amount			$ 180,000,000
First Stamford Place - First Lien | Mortgages
Debt Instrument [Line Items]
Stated Rate	4.09%		4.09%
Face amount	$ 164,000,000		$ 164,000,000
First Stamford Place - Second Lien | Mortgages
Debt Instrument [Line Items]
Stated Rate	6.25%		6.25%
Face amount	$ 16,000,000		$ 16,000,000
1010 Third Avenue and 77 West 55th Street | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 39,885,000					26,502,000
Stated Rate	4.01%		4.01%
Effective Rate	4.45%
Face amount			$ 40,000,000
10 Bank Street | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 34,802,000					31,544,000
Stated Rate	4.23%			4.23%
Effective Rate	4.54%
Face amount				$ 35,000,000
383 Main Avenue | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 30,000,000					28,654,000
Stated Rate	4.44%		4.44%
Effective Rate	4.77%
Face amount			$ 30,000,000
Senior unsecured notes - exchangeable | Convertible debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 250,000,000					250,000,000
Stated Rate	2.625%						2.625%
Effective Rate	3.93%
Face amount							$ 250,000,000
Senior unsecured notes, Series A | Senior notes
Debt Instrument [Line Items]
Total	$ 100,000,000					100,000,000
Stated Rate	3.93%
Effective Rate	4.00%
Senior unsecured notes, Series B | Senior notes
Debt Instrument [Line Items]
Total	$ 125,000,000					125,000,000
Stated Rate	4.09%
Effective Rate	4.17%
Senior unsecured notes, Series C | Senior notes
Debt Instrument [Line Items]
Total	$ 125,000,000					125,000,000
Stated Rate	4.18%
Effective Rate	4.26%
Unsecured revolving credit facility | Revolving credit facility
Debt Instrument [Line Items]
Unsecured facility	$ 0					0
Effective Rate	2.33%
Unsecured revolving credit facility | Revolving credit facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.10%
Unsecured term loan facility | Revolving credit facility
Debt Instrument [Line Items]
Unsecured facility	$ 265,000,000	$ 265,000,000				$ 265,000,000
Stated Rate	3.35%
Pay rate (as a percent)		2.1485%
Unsecured term loan facility | Revolving credit facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.20%

Debt - Mortgage Debt (Details)

Debt - Mortgage Debt (Details) - Mortgages - USD ($)	Sep. 30, 2017	Jun. 30, 2017	May 31, 2017	Apr. 30, 2017
1542 Third Avenue
Debt Instrument [Line Items]
Face amount				$ 30,000,000
Stated rate (as a percent)	4.29%			4.29%
10 Bank Street
Debt Instrument [Line Items]
Face amount			$ 35,000,000
Stated rate (as a percent)	4.23%		4.23%
First Stamford Place
Debt Instrument [Line Items]
Face amount		$ 180,000,000
Stated rate (as a percent)	4.28%	4.28%
First Stamford Place - First Lien
Debt Instrument [Line Items]
Face amount	$ 164,000,000	$ 164,000,000
Stated rate (as a percent)	4.09%	4.09%
First Stamford Place - Second Lien
Debt Instrument [Line Items]
Face amount	$ 16,000,000	$ 16,000,000
Stated rate (as a percent)	6.25%	6.25%
1010 Third Avenue and 77 West 55th Street
Debt Instrument [Line Items]
Face amount		$ 40,000,000
Stated rate (as a percent)	4.01%	4.01%
383 Main Avenue
Debt Instrument [Line Items]
Face amount		$ 30,000,000
Stated rate (as a percent)	4.44%	4.44%

Debt - Aggregate Required Princ

Debt - Aggregate Required Principal Payments (Details) - Mortgages - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortization
2017, amortization	$ 1,983
2018, amortization	4,417
2019, amortization	3,790
2020, amortization	3,938
2021, amortization	4,090
Thereafter	43,407
Total amortization	61,625
Maturities
2017, maturities	0
2018, maturities	262,210
2019, maturities	250,000
2020, maturities	0
2021, maturities	0
Thereafter	1,014,386
Total maturities	1,526,596
Total long term debt
2,017	1,983
2,018	266,627
2,019	253,790
2,020	3,938
2,021	4,090
Thereafter	1,057,793
Total	$ 1,588,221	$ 1,617,840

Debt - Deferred Financing Costs

Debt - Deferred Financing Costs, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Financing costs	$ 23,333		$ 23,333		$ 23,145
Less: accumulated amortization	(6,004)		(6,004)		(12,241)
Total deferred financing costs, net	17,329		17,329		10,904
Amortization of deferred financing costs	1,000	$ 1,300	3,600	$ 3,700
Revolving credit facility | Unsecured revolving credit facility
Debt Instrument [Line Items]
Net deferred financing costs	$ 8,700		$ 8,700		$ 4,500

Debt - Unsecured Revolving Cred

Debt - Unsecured Revolving Credit and Term Loan Facility (Details)	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2017USD ($)option	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Loss on early extinguishment of debt		$ 2,157,000	$ 0	$ 2,157,000	$ 552,000
Unsecured facility		0		0		$ 0
Unsecured Revolving Credit Facility and Term Loan | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,365,000,000
Unsecured revolving credit facility higher borrowing capacity option	1,750,000,000
Unsecured revolving credit facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 1,100,000,000
Unsecured facility		0		0		0
Number of options to extend maturity | option	2
Extension period	6 months
Unsecured term loan facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 265,000,000
Unsecured facility	$ 265,000,000	$ 265,000,000		$ 265,000,000		$ 265,000,000
Minimum | Unsecured revolving credit facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Extension fee, as a percent of outstanding commitments under revolving credit facility	0.0625%
Maximum | Unsecured revolving credit facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Extension fee, as a percent of outstanding commitments under revolving credit facility	0.075%

Debt - Exchangeable Senior Note

Debt - Exchangeable Senior Notes (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Aug. 31, 2014USD ($)$ / shares
Debt Instrument [Line Items]
Amortization of deferred financing costs	$ 1,000,000	$ 1,300,000	$ 3,600,000	$ 3,700,000
Convertible debt | Exchangeable Senior Notes due August 15, 2019
Debt Instrument [Line Items]
Face amount					$ 250,000,000
Stated rate (as a percent)	2.625%		2.625%		2.625%
Shares converted (in shares)			0.0517101
Conversion price (in USD per share) | $ / shares					$ 19.34
Debt interest expense	$ 2,400,000	2,400,000	$ 7,300,000	7,300,000
Contractual interest expense	1,600,000	1,600,000	4,900,000	4,900,000
Accretion of debt discount	700,000	700,000	2,000,000	2,000,000
Amortization of deferred financing costs	$ 100,000	$ 100,000	$ 400,000	$ 400,000

Accounts Payable and Accrued 39

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable and accrued expenses	$ 106,420	$ 102,866
Payable to the estate of Leona M. Helmsley	18,367	18,367
Interest rate swap agreements liability	13,378	5,591
Accrued interest payable	3,903	6,230
Due to affiliated companies	622	1,010
Accounts payable and accrued expenses	$ 142,690	$ 134,064

Financial Instruments and Fai40

Financial Instruments and Fair Values - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 13,378,000		$ 13,378,000		$ 5,591,000
Unrealized gain (loss) on valuation of interest rate swap agreements	(1,279,000)	$ 930,000	(14,252,000)	$ (29,305,000)
Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	13,400,000		13,400,000
Designated as Hedging Instrument | Cash Flow Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on valuation of interest rate swap agreements	(1,600,000)	$ 900,000	(14,700,000)	$ (29,300,000)
Amount expected to be reclassified within twelve months			2,900,000
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount	790,000,000		790,000,000
Accounts payable and accrued expenses | Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 13,400,000		$ 13,400,000		5,600,000
Prepaid expenses and other assets | Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements asset					$ 600,000

Financial Instruments and Fai41

Financial Instruments and Fair Values - Summary of the Terms of Agreements and the Fair Value of Derivative Financial Instruments (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Loss from derivative financial instruments	$ 0	$ 0	$ 289,000	$ 0
Cash Flow Hedging | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset	0		0			$ 614,000
Liability	(13,378,000)		(13,378,000)			(5,591,000)
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, One Month LIBOR, 2.1485%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 265,000,000		$ 265,000,000
Pay Rate (as a percent)	2.1485%		2.1485%
Asset	$ 0		$ 0			0
Liability	(3,436,000)		(3,436,000)			(1,634,000)
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Two Interest Rate Swaps, Three Month LIBOR, 2.5050%
Derivatives, Fair Value [Line Items]
Notional amount, terminated					$ 180,000,000
Deferred losses on terminated hedges	5,900,000		5,900,000
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.5050%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000		$ 100,000,000
Pay Rate (as a percent)	2.505%		2.505%
Asset	$ 0		$ 0			0
Liability	0		0			(684,000)
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.5050%, 2
Derivatives, Fair Value [Line Items]
Notional Amount	$ 80,000,000		$ 80,000,000		100,000,000
Pay Rate (as a percent)	2.505%		2.505%
Asset	$ 0		$ 0			0
Liability	0		0			(685,000)
Notional amount, terminated					$ 20,000,000
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.4860%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000		$ 100,000,000
Pay Rate (as a percent)	2.486%		2.486%
Asset	$ 0		$ 0			224,000
Liability	(1,448,000)		(1,448,000)			0
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.4860%, 2
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000		$ 100,000,000
Pay Rate (as a percent)	2.486%		2.486%
Asset	$ 0		$ 0			223,000
Liability	(1,448,000)		(1,448,000)			0
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.4860%, 3
Derivatives, Fair Value [Line Items]
Notional Amount	$ 75,000,000		$ 75,000,000
Pay Rate (as a percent)	2.486%		2.486%
Asset	$ 0		$ 0			167,000
Liability	(1,086,000)		(1,086,000)			0
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.7620%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 75,000,000		$ 75,000,000
Pay Rate (as a percent)	2.762%		2.762%
Asset	$ 0		$ 0			0
Liability	(2,592,000)		(2,592,000)			(1,295,000)
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.7620%, 2
Derivatives, Fair Value [Line Items]
Notional Amount	$ 75,000,000		$ 75,000,000
Pay Rate (as a percent)	2.762%		2.762%
Asset	$ 0		$ 0			0
Liability	(2,591,000)		(2,591,000)			(1,293,000)
LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.4625%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000		$ 100,000,000
Pay Rate (as a percent)	2.46245%		2.46245%
Asset	$ 0		$ 0			0
Liability	(777,000)		(777,000)			$ 0
Other expense | LIBOR | Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap, Three Month LIBOR, 2.5050%, 2
Derivatives, Fair Value [Line Items]
Loss from derivative financial instruments	$ 0	$ 0	$ 300,000	$ 0

Financial Instruments and Fai42

Financial Instruments and Fair Values - Effect of Derivative Financial Instruments Designated as Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ (16,890)	$ (17,939)	$ (52,109)	$ (52,758)
Designated as Hedging Instrument | Interest Rate Swap | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income (loss)	(1,638)	930	(14,654)	(29,305)
Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense	(359)	0	(402)	0
Accumulated net gain (loss) from cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ (359)	$ 0	$ (402)	$ 0

Financial Instruments and Fai43

Financial Instruments and Fair Values - Summary of the Carrying and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in accounts payable and accrued expenses	$ 13,378	$ 5,591
Mortgages | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	720,830	759,016
Mortgages | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	712,365	755,640
Senior Notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	348,991	348,914
Senior Notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	344,267	339,274
Senior unsecured notes - exchangeable | Exchangeable notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	243,923	241,474
Senior unsecured notes - exchangeable | Exchangeable notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	281,068	282,435
Fair Value, Inputs, Level 1 | Mortgages | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value, Inputs, Level 1 | Senior Notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value, Inputs, Level 1 | Senior unsecured notes - exchangeable | Exchangeable notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value, Inputs, Level 2 | Mortgages | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value, Inputs, Level 2 | Senior Notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value, Inputs, Level 2 | Senior unsecured notes - exchangeable | Exchangeable notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	281,068	282,435
Fair Value, Inputs, Level 3 | Mortgages | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	712,365	755,640
Fair Value, Inputs, Level 3 | Senior Notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	344,267	339,274
Fair Value, Inputs, Level 3 | Senior unsecured notes - exchangeable | Exchangeable notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Revolving Credit Facility | Unsecured term loan facility | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	263,546	262,927
Revolving Credit Facility | Unsecured term loan facility | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Revolving Credit Facility | Fair Value, Inputs, Level 1 | Unsecured term loan facility | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 2 | Unsecured term loan facility | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 3 | Unsecured term loan facility | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Interest Rate Swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in accounts payable and accrued expenses	13,400
Interest Rate Swap | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	614
Interest rate swaps included in accounts payable and accrued expenses	13,378	5,591
Interest Rate Swap | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	614
Interest rate swaps included in accounts payable and accrued expenses	13,378	5,591
Interest Rate Swap | Fair Value, Inputs, Level 1 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	0
Interest rate swaps included in accounts payable and accrued expenses	0	0
Interest Rate Swap | Fair Value, Inputs, Level 2 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	614
Interest rate swaps included in accounts payable and accrued expenses	13,378	5,591
Interest Rate Swap | Fair Value, Inputs, Level 3 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	0
Interest rate swaps included in accounts payable and accrued expenses	$ 0	$ 0

Rental Income - Narrative (Deta

Rental Income - Narrative (Details)	9 Months Ended
	Sep. 30, 2017
Minimum
Operating Leases [Line Items]
Term of lease	1 year
Maximum
Operating Leases [Line Items]
Term of lease	16 years

Commitments and Contingencies

Commitments and Contingencies - Legal Proceedings (Details)	Oct. 14, 2014participant
New York State Supreme Court, New York County
Loss Contingencies [Line Items]
Number of plaintiffs opting out of settlement	12

Commitments and Contingencies46

Commitments and Contingencies - Unfunded Capital Expenditures (Details) $ in Millions	Sep. 30, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Unfunded capital expenditures	$ 78.2

Commitments and Contingencies47

Commitments and Contingencies - Aggregate Required Payments on Ground Leases (Details) - Ground leases $ in Thousands	Sep. 30, 2017USD ($)
Operating Leased Assets [Line Items]
2,017	$ 380
2,018	1,518
2,019	1,518
2,020	1,518
2,021	1,518
Thereafter	55,212
Aggregate required payments on ground leases	$ 61,664

Capital - Narrative (Details)

Capital - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 23, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Class of Stock [Line Items]
Gross proceeds from sale of shares		$ 0	$ 611,278	$ 621,800
Shares and Units [Abstract]
OP units outstanding (in shares)		300,416,821
OP units owned by the Company (in shares)		159,427,448
OP units owned by the Company (as a percent)		53.10%
OP units not owned by the Company (in shares)		140,989,373
OP units not owned by the Company (as a percent)		46.90%
Dividends on common stock received until performance criteria met for LTIP units (as a percent)		10.00%
Dividends on common stock received after performance criteria met for LTIP units (as a percent)		90.00%
Dividends on common stock received in periods after performance criteria met for LTIP units (as a percent)		100.00%
Series PR operating partnership units
Shares and Units [Abstract]
OP units not owned by the Company (in shares)		93,203,688		93,075,441
Common shares | Common class A shares
Class of Stock [Line Items]
Issuance of common shares (in shares)				29,610,854
Common shares issued (in dollars per share)				$ 21
General partner | Series PR operating partnership units
Class of Stock [Line Items]
Issuance of common shares (in shares)	29,610,854			29,610,854
QIA
Class of Stock [Line Items]
Economic interest held by QIA	9.90%

Capital - Distributions (Detail

Capital - Distributions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note Disclosure, Disclosure of Compensation Related Costs, Share-based Payments and Earnings Per Share [Abstract]
Distributions paid to OP unitholders	$ 31.5	$ 31.4	$ 94.5	$ 82.6
Distributions paid to preferred unitholders	$ 0.2	$ 0.2	$ 0.7	$ 0.7

Capital - Incentive and Share-b

Capital - Incentive and Share-based Compensation (Details) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2017USD ($)shares	Mar. 31, 2017USD ($)vesting_installmentshares	Jun. 30, 2016USD ($)shares	Feb. 29, 2016USD ($)vesting_installmentshares	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2016USD ($)$ / shares	Dec. 31, 2016USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average per unit or share fair value (in USD per share) | $ / shares							$ 13.77
Expected volatility rate look-back period							6 years
Age of grantee at which LTIP unit and restricted stock awards immediately vest							60 years
Period of service, upon completion of which, grantee's LTIP unit and restricted stock awards will immediately vest							10 years
Awards that Meet Age and Service Requirements for Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Noncash share-based compensation expense recognized | $					$ 0.2	$ 0.1	$ 0.9	$ 0.6
Unrecognized compensation expense | $					0.9		$ 0.9
Unrecognized compensation expense, period for recognition							2 years 5 months 12 days
Awards that Do Not Meet Age and Service Requirements for Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Noncash share-based compensation expense recognized | $					3.7	$ 2.5	$ 9.9	6.7
Unrecognized compensation expense | $					$ 26.5		$ 26.5
Unrecognized compensation expense, period for recognition							2 years 5 months 18 days
Long-Term Incentive Plan Units and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $							$ 19.4	$ 18.4
Weighted-average per unit or share fair value (in USD per share) | $ / shares							$ 13.77	$ 9.60
Risk free interest rate (as a percent)							1.55%	0.84%
Expected volatility rate (as a percent)							20.00%	24.00%
LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares							1,372,574
Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares		47,993		47,168
Fair value of share-based awards granted in period | $		$ 1.6		$ 1.4					$ 0.1
Performance Based Long-Term Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares		95,156		112,925
Fair value of share-based awards granted in period | $		$ 1		$ 0.8
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares							34,407
Time Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares		34,407		44,198
Long-Term Incentive Plan Unit and Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term							2 years 9 months 18 days	2 years 9 months 18 days
Dividend rate (as a percent)							2.05%	2.10%
Executive Officer | Time Based Long-Tern Incentive Plan Unit | 2013 Plan Units, granted in March 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares		313,275
Fair value of share-based awards granted in period | $		$ 6.1
Number of vesting installments | vesting_installment		3
Award vesting period		4 years
Executive Officer | Time Based Long-Tern Incentive Plan Unit | 2013 Plan Units Vesting January 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares				368,225
Fair value of share-based awards granted in period | $				$ 5.6
Number of vesting installments | vesting_installment				3
Award vesting period				4 years
Executive Officer | Time Based Long-Tern Incentive Plan Unit | 2013 Plan Units Vesting three years after February 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares				62,814
Fair value of share-based awards granted in period | $				$ 1
Award vesting percentage after three years				30.00%
Award vesting percentage after four years				30.00%
Award vesting percentage after five years				40.00%
Executive Officer | Performance Based Long-Term Incentive Plan Unit | 2013 Plan Units, granted in March 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares		865,742
Fair value of share-based awards granted in period | $		$ 9.6
Number of vesting installments | vesting_installment		2
Award vesting period		3 years
Executive Officer | Performance Based Long-Term Incentive Plan Unit | 2013 Plan Units Vesting January 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares				1,230,228
Fair value of share-based awards granted in period | $				$ 8.8
Number of vesting installments | vesting_installment				2
Award vesting period				3 years
Director | Time Based Long-Tern Incentive Plan Unit | 2013 Plan Units, granted In May 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares	50,408
Fair value of share-based awards granted in period | $	$ 1
Award vesting period	3 years
Director | Time Based Long-Tern Incentive Plan Unit | 2013 Plan Units Vesting three years after June 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares) | shares			43,257
Fair value of share-based awards granted in period | $			$ 0.8
Award vesting period			3 years
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under the plan (in shares) | shares					12,200,000		12,200,000
Number of shares that remain available for future issuance (in shares) | shares					7,000,000		7,000,000

Capital - Summary of ESRT Restr

Capital - Summary of ESRT Restricted Stock and LTIP Unit Activity (Details)	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Weighted Average Grant Fair Value [Roll Forward]
Beginning balance, Unvested, Weighted Average Grant Fair Value (in USD per share) | $ / shares	$ 10.01
Vested, Weighted Average Grant Fair Value (in USD per share) | $ / shares	13.74
Granted, Weighted Average Grant Fair Value (in USD per share) | $ / shares	13.77
Forfeited or unearned, Weighted Average Grant Fair Value (in USD per share) | $ / shares	5.36
Ending balance, Unvested, Weighted Average Grant Fair Value (in USD per share) | $ / shares	$ 11.11
Restricted Stock
Restricted Stock and LTIP Unit Activity [Roll Forward]
Beginning balance, Unvested (in shares)	107,793
Vested (in shares)	(17,923)
Granted (in shares)	34,407
Forfeited or unearned (in shares)	(2,509)
Ending balance, Unvested (in shares)	121,768
LTIP Units
Restricted Stock and LTIP Unit Activity [Roll Forward]
Beginning balance, Unvested (in shares)	2,881,629
Vested (in shares)	(323,982)
Granted (in shares)	1,372,574
Forfeited or unearned (in shares)	(77,227)
Ending balance, Unvested (in shares)	3,852,994

Capital - Earnings Per Unit (De

Capital - Earnings Per Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income	$ 35,489	$ 32,897	$ 85,993	$ 74,242
Private perpetual preferred unit distributions	(234)	(234)	(702)	(702)
Earnings allocated to unvested units	(228)	(225)	(582)	(575)
Net income attributable to common unitholders - basic and diluted	$ 35,027	$ 32,438	$ 84,709	$ 72,965
Denominator:
Weighted average units outstanding - basic (in units)	296,389,000	278,739,000	296,389,000	270,388,000
Effect of dilutive securities:
Effect of dilutive securities - stock-based compensation plans (in units)	762,000	1,090,000	848,000	378,000
Effect of dilutive securities - exchangeable senior notes (in units)	720,000	785,000	852,000	262,000
Weighted average units outstanding - diluted (in units)	297,871,000	280,614,000	298,089,000	271,028,000
Earnings per share:
Basic earnings (in USD per unit)	$ 0.12	$ 0.12	$ 0.29	$ 0.27
Diluted earnings (in USD per unit)	$ 0.12	$ 0.12	$ 0.28	$ 0.27
Antidilutive securities (in units)	954,533	1,033,044	840,092	757,119

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2016ft²property	Sep. 30, 2017USD ($)ft²director	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)ft²director	Sep. 30, 2016USD ($)	Jul. 31, 2016ft²property
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | ft²		10,100,000		10,100,000
Number of directors | director		1		1
Affliliated entity | Supervisory fee revenue
Related Party Transaction [Line Items]
Revenue from related parties		$ 300	$ 300	$ 900	$ 1,100
Affliliated entity | Property management fee revenue
Related Party Transaction [Line Items]
Revenue from related parties		100	100	200	300
Affliliated entity | Leased space rental
Related Party Transaction [Line Items]
Revenue from related parties			$ 70		200
Area of real estate property (in square feet) | ft²						3,074
Number of properties | property	1					1
Lease cancellation, notice period	90 days
Affliliated entity | Annualized rent revenue
Related Party Transaction [Line Items]
Revenue from related parties				5,800	$ 5,700
Undivided Interest
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | ft²	5,351					647
Chairman emeritus | Leased space rental
Related Party Transaction [Line Items]
Percentage of lease space occupied by Chairman emeritus and employee	15.00%
Revenue from revenue parties, net of payment for pro rata share of leased space		$ 100		$ 300

Segment Reporting - Narrative

Segment Reporting - Narrative (Details)	9 Months Ended
	Sep. 30, 2017segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Reporting - Components

Segment Reporting - Components of Segment Profit for Each Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Revenues:
Rental revenue	$ 122,391	$ 115,634	$ 360,348	$ 343,155
Intercompany rental revenue	0	0	0	0
Tenant expense reimbursement	20,346	19,176	53,889	56,350
Observatory revenue	39,306	38,093	94,212	91,112
Third-party management and other fees	345	404	1,088	1,372
Other revenue and fees	4,932	2,541	19,861	6,748
Total revenues	187,320	175,848	529,398	498,737
Operating expenses:
Property operating expenses	41,270	38,585	122,009	115,075
Intercompany rent expense	0	0	0	0
Ground rent expenses	2,331	2,331	6,994	6,994
General and administrative expenses	12,899	11,798	36,566	35,623
Observatory expenses	8,648	7,250	23,079	21,900
Real estate taxes	26,901	24,691	76,001	71,773
Acquisition expenses	0	0	0	98
Depreciation and amortization	38,490	37,607	119,868	115,382
Total operating expenses	130,539	122,262	384,517	366,845
Total operating income	56,781	53,586	144,881	131,892
Other expenses:
Interest expense	(16,890)	(17,939)	(52,109)	(52,758)
Loss on early extinguishment of debt	(2,157)	0	(2,157)	(552)
Loss from derivative financial instruments	0	0	(289)	0
Income before income taxes	37,734	35,647	90,326	78,582
Income tax expense	(2,245)	(2,750)	(4,333)	(4,340)
Net income	35,489	32,897	85,993	74,242
Segment assets	3,848,934	3,882,569	3,848,934	3,882,569	$ 3,890,953
Expenditures for segment assets	53,731	52,828	163,115	140,099
Intersegment Elimination
Revenues:
Rental revenue	0	0	0	0
Intercompany rental revenue	(23,301)	(22,983)	(57,354)	(55,189)
Tenant expense reimbursement	0	0	0	0
Observatory revenue	0	0	0	0
Third-party management and other fees	0	0	0	0
Other revenue and fees	0	0	0	0
Total revenues	(23,301)	(22,983)	(57,354)	(55,189)
Operating expenses:
Property operating expenses	0	0	0	0
Intercompany rent expense	(23,301)	(22,983)	(57,354)	(55,189)
Ground rent expenses	0	0	0	0
General and administrative expenses	0	0	0	0
Observatory expenses	0	0	0	0
Real estate taxes	0	0	0	0
Acquisition expenses		0	0	0
Depreciation and amortization	0	0	0	0
Total operating expenses	(23,301)	(22,983)	(57,354)	(55,189)
Total operating income	0	0	0	0
Other expenses:
Interest expense	0	0	0	0
Loss on early extinguishment of debt	0	0	0	0
Loss from derivative financial instruments	0	0	0	0
Income before income taxes	0	0	0	0
Income tax expense	0	0	0	0
Net income	0	0	0	0
Segment assets	0	0	0	0
Expenditures for segment assets	0	0	0	0
Real Estate | Operating Segments
Revenues:
Rental revenue	122,391	115,634	360,348	343,155
Intercompany rental revenue	23,301	22,983	57,354	55,189
Tenant expense reimbursement	20,346	19,176	53,889	56,350
Observatory revenue	0	0	0	0
Third-party management and other fees	345	404	1,088	1,372
Other revenue and fees	4,932	2,536	19,861	6,738
Total revenues	171,315	160,733	492,540	462,804
Operating expenses:
Property operating expenses	41,270	38,585	122,009	115,075
Intercompany rent expense	0	0	0	0
Ground rent expenses	2,331	2,331	6,994	6,994
General and administrative expenses	12,899	11,798	36,566	35,623
Observatory expenses	0	0	0	0
Real estate taxes	26,901	24,691	76,001	71,773
Acquisition expenses		0	0	98
Depreciation and amortization	38,473	37,421	119,764	115,002
Total operating expenses	121,874	114,826	361,334	344,565
Total operating income	49,441	45,907	131,206	118,239
Other expenses:
Interest expense	(16,890)	(17,939)	(52,109)	(52,758)
Loss on early extinguishment of debt	(2,157)	0	(2,157)	(552)
Loss from derivative financial instruments	0	0	(289)	0
Income before income taxes	30,394	27,968	76,651	64,929
Income tax expense	(264)	(332)	(960)	(1,018)
Net income	30,130	27,636	75,691	63,911
Segment assets	3,582,935	3,636,262	3,582,935	3,636,262
Expenditures for segment assets	40,320	52,828	142,854	140,052
Observatory | Operating Segments
Revenues:
Rental revenue	0	0	0	0
Intercompany rental revenue	0	0	0	0
Tenant expense reimbursement	0	0	0	0
Observatory revenue	39,306	38,093	94,212	91,112
Third-party management and other fees	0	0	0	0
Other revenue and fees	0	5	0	10
Total revenues	39,306	38,098	94,212	91,122
Operating expenses:
Property operating expenses	0	0	0	0
Intercompany rent expense	23,301	22,983	57,354	55,189
Ground rent expenses	0	0	0	0
General and administrative expenses	0	0	0	0
Observatory expenses	8,648	7,250	23,079	21,900
Real estate taxes	0	0	0	0
Acquisition expenses		0	0	0
Depreciation and amortization	17	186	104	380
Total operating expenses	31,966	30,419	80,537	77,469
Total operating income	7,340	7,679	13,675	13,653
Other expenses:
Interest expense	0	0	0	0
Loss on early extinguishment of debt	0	0	0	0
Loss from derivative financial instruments	0	0	0	0
Income before income taxes	7,340	7,679	13,675	13,653
Income tax expense	(1,981)	(2,418)	(3,373)	(3,322)
Net income	5,359	5,261	10,302	10,331
Segment assets	265,999	246,307	265,999	246,307
Expenditures for segment assets	$ 13,411	$ 0	$ 20,261	$ 47