Empire State Realty Trust (ESRT) 10-Q 3 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Entity Registrant Name	Empire State Realty Trust, Inc.
Entity Central Index Key	1,541,401
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Filer Category	Large Accelerated Filer
Class A Common Stock
Entity Common Stock, Shares Outstanding		164,463,762
Class B Common Stock
Entity Common Stock, Shares Outstanding		1,047,473

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Commercial real estate properties, at cost:
Land	$ 201,196	$ 201,196
Development costs	7,986	7,986
Building and improvements	2,495,901	2,458,473
Commercial real estate properties, at cost, gross	2,705,083	2,667,655
Less: accumulated depreciation	(678,250)	(656,900)
Commercial real estate properties, net	2,026,833	2,010,755
Cash and cash equivalents	690,471	464,344
Restricted cash	61,699	65,853
Tenant and other receivables, net of allowance of $1,128 and $1,422 in 2018 and 2017, respectively	25,156	28,329
Deferred rent receivables, net of allowance of $0 and $185 in 2018 and 2017, respectively	184,667	178,629
Prepaid expenses and other assets	39,393	61,028
Deferred costs, net	255,844	262,701
Acquired below-market ground leases, net	366,271	368,229
Goodwill	491,479	491,479
Total assets	4,141,813	3,931,347
Liabilities:
Mortgage notes payable, net	610,826	717,164
Senior unsecured notes, net	1,043,677	707,895
Unsecured term loan facility, net	263,777	263,662
Unsecured revolving credit facility	0	0
Accounts payable and accrued expenses	106,830	110,849
Acquired below-market leases, net	62,418	66,047
Deferred revenue and other liabilities	37,499	40,907
Tenants’ security deposits	43,448	47,086
Total liabilities	2,168,475	1,953,610
Commitments and contingencies
Empire State Realty Trust, Inc. stockholders' equity:
Preferred stock	0	0
Additional paid-in capital	1,138,600	1,128,460
Accumulated other comprehensive loss	(6,037)	(8,555)
Retained earnings	39,323	46,762
Total Empire State Realty Trust, Inc.'s stockholders' equity	1,173,529	1,168,282
Non-controlling interests in operating partnership	791,805	801,451
Private perpetual preferred units, $16.62 per unit liquidation preference, 1,560,360 issued and outstanding in 2018 and 2017	8,004	8,004
Total equity	1,973,338	1,977,737
Total liabilities and equity	4,141,813	3,931,347
Class A Common Stock
Empire State Realty Trust, Inc. stockholders' equity:
Common stock	1,633	1,604
Class B Common Stock
Empire State Realty Trust, Inc. stockholders' equity:
Common stock	$ 10	$ 11

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Tenant and other receivables allowance	$ 1,128	$ 1,422
Deferred rent receivables allowance	$ 0	$ 185
Equity:
Preferred stock, par value (in USD per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Private perpetual preferred units, per unit 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
Class A Common Stock
Equity:
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	163,321,049	160,424,575
Common stock, shares outstanding (in shares)	163,321,049	160,424,575
Class B Common Stock
Equity:
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	1,048,161	1,052,469
Common stock, shares outstanding (in shares)	1,048,161	1,052,469

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Rental revenue	$ 122,311	$ 117,113
Tenant expense reimbursement	17,794	15,974
Observatory revenue	21,249	20,940
Lease termination fees	622	7,938
Third-party management and other fees	463	351
Other revenue and fees	6,057	2,638
Total revenues	168,496	164,954
Operating expenses:
Property operating expenses	44,185	42,210
Ground rent expenses	2,331	2,331
General and administrative expenses	12,628	11,088
Observatory expenses	7,336	7,255
Real estate taxes	26,744	24,558
Depreciation and amortization	39,883	40,846
Total operating expenses	133,107	128,288
Total operating income	35,389	36,666
Other expenses:
Interest expense	(17,591)	(17,742)
Loss from derivative financial instruments	0	(247)
Income before income taxes	17,798	18,677
Income tax benefit	260	468
Net income	18,058	19,145
Private perpetual preferred unit distributions	(234)	(234)
Net income attributable to non-controlling interests	(8,056)	(8,926)
Net income attributable to common stockholders	$ 9,768	$ 9,985
Total weighted average shares:
Basic (in shares)	162,667	156,493
Diluted (in shares)	296,827	297,962
Earnings per share attributable to common stockholders:
Basic (in USD per share)	$ 0.06	$ 0.06
Diluted (in USD per share)	0.06	0.06
Dividends per share (in USD per share)	$ 0.105	$ 0.105

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 18,058	$ 19,145
Other comprehensive income:
Unrealized gain on valuation of interest rate swap agreements	4,180	1,394
Less amount reclassified into interest expense	599	0
Other comprehensive income	4,779	1,394
Comprehensive income	22,837	20,539
Net income attributable to non-controlling interests and private perpetual preferred unitholders	(8,290)	(9,160)
Other comprehensive income attributable to non-controlling interests	(2,160)	(658)
Comprehensive income attributable to common stockholders	$ 12,387	$ 10,721

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Stockholders' Equity (unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Class A Common Stock	Class B Common Stock	Common StockClass A Common Stock	Common StockClass B Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total Stockholders' Equity	Non-controlling Interests	Private Perpetual Preferred Units
Beginning balance (in shares) at Dec. 31, 2017		160,424,575	1,052,469	160,425,000	1,052,000
Beginning balance at Dec. 31, 2017	$ 1,977,737			$ 1,604	$ 11	$ 1,128,460	$ (8,555)	$ 46,762	$ 1,168,282	$ 801,451	$ 8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				2,870,000	(4,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 29	$ (1)	10,162	(101)		10,089	(10,089)
Equity compensation:
LTIP units	4,577									4,577
Restricted stock, net of forfeitures (in shares)				26,000
Restricted stock, net of forfeitures	(22)					(22)			(22)
Dividends and distributions	(31,791)							(17,207)	(17,207)	(14,350)	(234)
Net income	18,058							9,768	9,768	8,056	234
Other comprehensive income (loss)	4,779						2,619		2,619	2,160
Ending balance (in shares) at Mar. 31, 2018		163,321,049	1,048,161	163,321,000	1,048,000
Ending balance at Mar. 31, 2018	$ 1,973,338			$ 1,633	$ 10	$ 1,138,600	$ (6,037)	$ 39,323	$ 1,173,529	$ 791,805	$ 8,004

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows From Operating Activities
Net income	$ 18,058	$ 19,145
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	39,883	40,846
Amortization of non-cash items within interest expense	993	225
Amortization of acquired above- and below-market leases, net	(1,168)	(1,428)
Amortization of acquired below-market ground leases	1,958	1,958
Straight-lining of rental revenue	(5,853)	(5,931)
Equity based compensation	4,555	3,154
Unrealized loss from derivative financial instruments	0	104
Increase (decrease) in cash flows due to changes in operating assets and liabilities:
Security deposits	(3,637)	15
Tenant and other receivables	2,989	1,963
Deferred leasing costs	(7,372)	(7,733)
Prepaid expenses and other assets	25,738	17,867
Accounts payable and accrued expenses	(4,176)	(8,141)
Deferred revenue and other liabilities	(3,408)	(1,115)
Net cash provided by operating activities	68,560	60,929
Cash Flows From Investing Activities
Development costs	0	(26)
Additions to building and improvements	(44,112)	(47,040)
Net cash used in investing activities	(44,112)	(47,066)
Cash Flows From Financing Activities
Proceeds from mortgage notes payable	160,000	0
Repayment of mortgage notes payable	(263,863)	(3,167)
Proceeds from unsecured revolving credit facility and term loan	335,000	0
Deferred financing costs	(1,821)	(45)
Private perpetual preferred unit distributions	(234)	(234)
Dividends paid to common stockholders	(17,207)	(16,482)
Distributions paid to non-controlling interests in the operating partnership	(14,350)	(14,914)
Net cash provided (used in) by financing activities	197,525	(34,842)
Net increase (decrease) in cash and cash equivalents and restricted cash	221,973	(20,979)
Cash and cash equivalents and restricted cash—beginning of period	530,197	615,885
Cash and cash equivalents and restricted cash—end of period	752,170	594,906
Reconciliation of Cash and Cash Equivalents and Restricted Cash:
Cash and cash equivalents at beginning of period	464,344	554,371
Restricted cash at beginning of period	65,853	61,514
Cash and cash equivalents at end of period	690,471	532,442
Restricted cash at end of period	61,699	62,464
Supplemental disclosures of cash flow information:
Cash paid for interest	16,989	19,073
Cash paid for income taxes	659	507
Non-cash investing and financing activities:
Building and improvements included in accounts payable and accrued expenses	74,008	67,614
Derivative instruments at fair values included in prepaid expenses and other assets	4,103	1,547
Derivative instruments at fair values included in accounts payable and accrued expenses	0	5,234
Conversion of operating partnership units and Class B shares to Class A shares	$ 10,089	$ 7,809

Description of Business and Org

Description of Business and Organization	3 Months Ended
	Mar. 31, 2018
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,” the “company,” and "ESRT" mean Empire State Realty Trust, Inc. and its consolidated subsidiaries. We are a self-administered and self-managed real estate investment trust ("REIT") that owns, manages, operates, acquires and repositions office and retail properties in Manhattan and the greater New York metropolitan area. As of March 31, 2018 , 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 506,352 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. As of March 31, 2018 , our portfolio included four standalone retail properties located in Manhattan and two standalone retail properties located in the city center of Westport, Connecticut, encompassing 205,708 rentable square feet in the aggregate. We were organized as a Maryland corporation on July 29, 2011 and commenced operations upon completion of our initial public offering and related formation transactions on October 7, 2013. Our operating partnership, Empire State Realty OP, L.P. (the "Operating Partnership"), holds substantially all of our assets and conducts substantially all of our business. As of March 31, 2018 , we owned approximately 54.2% of the aggregate operating partnership units in the Operating Partnership. We, as the sole general partner in the Operating Partnership, have responsibility and discretion in the management and control of the Operating Partnership, and the limited partners in the Operating Partnership, in such capacity, have no authority to transact business for, or participate in the management activities of, the Operating Partnership. Accordingly, the Operating Partnership has been consolidated by us. We elected to be taxed as a REIT and operate in a manner that we believe allows us to qualify as a REIT for federal income tax purposes commencing with our taxable year ended December 31, 2013.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
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, 2017 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, 2017 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. The Operating Partnership is a variable interest entity of our company, Empire State Realty Trust, Inc. As the Operating Partnership is already consolidated in the financial statements of Empire State Realty Trust, Inc., the identification of this entity as a variable interest entity has no impact on our consolidated financial statements. 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 balances of other revenues and interest expense have been reclassified to separately present lease termination fees and loss on early extinguishment of debt, respectively. Recentl y Issued or Adopted Accounting Standards During January 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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 is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The amendments are applied prospectively on or after the effective date. No disclosures are required at transition. We believe that acquisitions of real estate properties will generally 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 is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. We adopted this standard on January 1, 2018 using a retrospective transition method. The adoption did not have a material impact 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 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. We adopted this standard on January 1, 2018 using a retrospective transition method. The adoption did not have a material impact 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 March 31, 2018 , the remaining contractual payments under our ground lease agreements aggregated $60.9 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 $2.6 million for the year ended December 31, 2017. 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 replaces 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. We adopted this standard on January 1, 2018 and it did not have a material impact on our consolidated financial statements.

Deferred Costs, Acquired Lease

Deferred Costs, Acquired Lease Intangibles and Goodwill	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Leasing costs $ 166,908 $ 164,751 Acquired in-place lease value and deferred leasing costs 227,086 237,364 Acquired above-market leases 63,191 67,415 457,185 469,530 Less: accumulated amortization (209,143 ) (215,102 ) Total deferred costs, net, excluding net deferred financing costs $ 248,042 $ 254,428 At March 31, 2018 and December 31, 2017, $7.8 million and $8.3 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 $ 6.2 million and $6.2 million for the three months ended March 31, 2018 and 2017, respectively. Amortization expense related to acquired lease intangibles was $3.4 million and $4.4 million for the three months ended March 31, 2018 and 2017, respectively. Amortizing acquired intangible assets and liabilities consisted of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Acquired below-market ground leases $ 396,916 $ 396,916 Less: accumulated amortization (30,645 ) (28,687 ) Acquired below-market ground leases, net $ 366,271 $ 368,229 March 31, 2018 December 31, 2017 Acquired below-market leases $ (124,615 ) $ (132,026 ) Less: accumulated amortization 62,197 65,979 Acquired below-market leases, net $ (62,418 ) $ (66,047 ) Rental revenue related to the amortization of below-market leases, net of above-market leases, was $1.2 million and $1.4 million for the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018 , 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	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt Debt consisted of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): Principal Balance As of March 31, 2018 March 31, 2018 December 31, 2017 Stated Effective (1) Maturity (2) Mortgage debt collateralized by: Fixed rate mortgage debt Metro Center $ 93,428 $ 93,948 3.59 % 3.68 % 11/5/2024 10 Union Square 50,000 50,000 3.70 % 3.97 % 4/1/2026 1542 Third Avenue 30,000 30,000 4.29 % 4.54 % 5/1/2027 First Stamford Place (3) 180,000 180,000 4.28 % 4.39 % 7/1/2027 1010 Third Avenue and 77 West 55th Street 39,534 39,710 4.01 % 4.22 % 1/5/2028 10 Bank Street 34,399 34,602 4.23 % 4.35 % 6/1/2032 383 Main Avenue 30,000 30,000 4.44 % 4.55 % 6/30/2032 1333 Broadway 160,000 66,602 4.21 % 4.21 % 2/5/2033 1400 Broadway (first lien mortgage loan) — 66,632 — — — (second lien mortgage loan) — 9,172 — — — 111 West 33rd Street (first lien mortgage loan) — 74,045 — — — (second lien mortgage loan) — 9,369 — — — 1350 Broadway — 37,144 — — — Total mortgage debt 617,361 721,224 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 % 3.96 % 3/27/2025 Series B 125,000 125,000 4.09 % 4.12 % 3/27/2027 Series C 125,000 125,000 4.18 % 4.21 % 3/27/2030 Series D 115,000 115,000 4.08 % 4.11 % 1/22/2028 Series E 160,000 — 4.26 % 4.26 % 3/22/2030 Series F 175,000 — 4.44 % 4.44 % 3/22/2033 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 1,932,361 1,701,224 Unamortized discount, net of unamortized premium (3,651 ) (3,370 ) Deferred financing costs, net (10,430 ) (9,133 ) Total $ 1,918,280 $ 1,688,721 ______________ (1) The effective rate is the yield as of March 31, 2018 , 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 at 4.09% and a $16 million loan bearing interest at 6.25% . (4) At March 31, 2018 , the unsecured revolving credit facility bears a floating rate at 30 day LIBOR plus 1.10% . The rate at March 31, 2018 was 2.98% . (5) The unsecured term loan facility bears a floating rate at 30 day LIBOR plus 1.20% . Pursuant to an interest rate swap agreement, the LIBOR rate is fixed at 2.1485% through maturity. The rate at March 31, 2018 was 3.35% . (6) At March 31, 2018 , we were in compliance with all debt covenants. Mortgage Debt During January 2018, we refinanced and increased our mortgage debt on 1333 Broadway from $66.6 million to $160.0 million , due February 2033 with interest fixed at 4.21% . A portion of this increase was applied to release the $75.8 million mortgage lien on 1400 Broadway. Principal Payments Aggregate required principal payments at March 31, 2018 are as follows (amounts in thousands): Year Amortization Maturities Total 2018 $ 2,749 $ — $ 2,749 2019 3,790 250,000 253,790 2020 3,938 — 3,938 2021 4,090 — 4,090 2022 5,628 265,000 270,628 Thereafter 41,744 1,355,422 1,397,166 Total $ 61,939 $ 1,870,422 $ 1,932,361 Deferred Financing Costs Deferred financing costs, net, consisted of the following at March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Financing costs $ 25,587 $ 24,446 Less: accumulated amortization (7,364 ) (7,039 ) Total deferred financing costs, net $ 18,223 $ 17,407 At March 31, 2018 and December 31, 2017, $7.8 million and $8.3 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 March 31, 2018 and 2017, respectively, and was included in interest expense. Unsecured Revolving Credit and Term Loan Facility During August 2017, through the Operating Partnership, 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 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. 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. The 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 March 31, 2018 , the exchange rate of the 2.625% Exchangeable Senior Notes was 51.8215 shares per $1,000 principal amount of notes (equivalent to an initial exchange price of approximately $19.30 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 months ended March 31, 2018 , total interest expense related to the 2.625% Exchangeable Senior Notes was $2.4 million consisting of (i) the contractual interest expense of $1.6 million , (ii) the additional non-cash interest expense of $0.7 million relating to the accretion of the debt discount, and (iii) the amortization of deferred financing costs of $0.1 million . For the three months ended March 31, 2017 , total interest expense related to the 2.625% Exchangeable Senior Notes was $2.4 million consisting of (i) the contractual interest expense of $1.6 million , (ii) the additional non-cash interest expense of $0.7 million relating to the accretion of the debt discount, and (iii) the amortization of deferred financing costs of $0.1 million . Senior Unsecured Notes During December 2017, we entered into an agreement to issue and sell an aggregate principal amount of $450.0 million of senior unsecured notes consisting of $115.0 million of 4.08% Series D Senior Notes due 2028, $160.0 million of 4.26% Series E Senior Notes due 2030, and $175.0 million of 4.44% Series F Senior Notes due 2033. We issued and sold the Series D Senior Notes in December 2017 and the Series E and F Senior Notes in March 2018. In connection with the March 2018 issuance of the notes, we repaid our mortgage indebtedness on 111 West 33rd Street and 1350 Broadway, before their maturity dates in early April 2018.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Accrued capital expenditures $ 74,008 $ 71,769 Accounts payable and accrued expenses 28,516 32,509 Interest rate swap agreements liability — 436 Accrued interest payable 3,642 5,687 Due to affiliated companies 664 448 Total accounts payable and accrued expenses $ 106,830 $ 110,849

Financial Instruments and Fair

Financial Instruments and Fair Values	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 , we did not have any derivatives in a net liability position. As of March 31, 2018 and December 31, 2017, we had one interest rate LIBOR swap with an aggregate notional value of $265.0 million . The notional value does not represent exposure to credit, interest rate or market risks. As of March 31, 2018 , the fair value of this derivative instrument amounted to $4.1 million which is included in prepaid expenses and other assets on the condensed consolidated balance sheet. As of December 31, 2017, the fair value of this derivative instrument amounted to ( $0.4 million ) which was included in accounts payable and accrued expenses on the condensed consolidated balance sheet. This interest rate swap has been designated as a cash flow hedge and hedges the future cash outflows on our term loan facility that is subject to a floating interest rate. As of March 31, 2018 and 2017, our cash flow hedges are deemed highly effective and a net unrealized gain of $4.8 million and $1.4 million for the three months ended March 31, 2018 and 2017, respectively, are reflected in the condensed consolidated statements of comprehensive income. 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 $0.04 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 contract in effect as of March 31, 2018 . As of March 31, 2018 and December 31, 2017, the deferred net losses from terminated hedges amounted to $14.8 million and $15.1 million , respectively, which are included in accumulated other comprehensive income (loss) related to derivatives. We will reclassify into earnings, as an increase to interest expense, approximately $1.5 million within the next 12 months related to the deferred losses from the terminated hedges. For the three months ended March 31, 2017, we also recognized a $0.2 million loss from derivative financial instruments incurred in connection with the partial termination and re-designation of related cash flow hedges on a $20.0 million notional amount. The table below summarizes the terms of the agreement and the fair value of our derivative financial instrument as of March 31, 2018 and December 31, 2017 (dollar amounts in thousands): March 31, 2018 December 31, 2017 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 $ 4,103 $ — $ — $ (436 ) $ 4,103 $ — $ — $ (436 ) 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 months ended March 31, 2018 and 2017 (amounts in thousands): Three Months Ended Effects of Cash Flow Hedges March 31, 2018 March 31, 2017 Amount of gain (loss) recognized in other comprehensive income (loss) $ 4,180 $ 1,394 Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (599 ) — The table below shows the effect of our derivative financial instruments designated as cash flow hedges on the condensed consolidated statements of income for the three months ended March 31, 2018 and 2017 (amounts in thousands): Three Months Ended Effects of Cash Flow Hedges March 31, 2018 March 31, 2017 Total interest (expense) presented in the condensed consolidated statements of income in which the effects of cash flow hedges are recorded $ (17,591 ) $ (17,742 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (599 ) — Fair Valuation The estimated fair values at March 31, 2018 and December 31, 2017 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, C, D, E and F, 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 March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 Estimated Fair Value Carrying Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ 4,103 $ 4,103 $ — $ 4,103 $ — Interest rate swaps included in accounts payable and accrued expenses — — — — — Mortgage notes payable 610,826 588,596 — — 588,596 Senior unsecured notes - Exchangeable 245,556 257,903 — 257,903 — Senior unsecured notes - Series A, B, C, D, E and F 798,121 791,005 — — 791,005 Unsecured term loan facility 263,777 265,000 — — 265,000 December 31, 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 436 436 — 436 — Mortgage notes payable 717,164 707,300 — — 707,300 Senior unsecured notes - Exchangeable 244,739 275,723 — 275,723 — Senior unsecured notes - Series A, B, C and D 463,156 460,352 — — 460,352 Unsecured term loan facility 263,662 265,000 — — 265,000 Disclosure about the fair value of financial instruments is based on pertinent information available to us as of March 31, 2018 and December 31, 2017. Although we are not aware of any factors that would significantly affect the reasonable fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since that date and current estimates of fair value may differ significantly from the amounts presented herein.

Rental Income

Rental Income	3 Months Ended
	Mar. 31, 2018
Leases [Abstract]
Rental Income	Rental Income We lease various spaces to tenants over terms ranging from one to 21 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	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings Except as described below, as of March 31, 2018 , 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, in October 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 (also filed later in federal court in New York for the expressed purpose of tolling the statute of limitations) alleges breach of fiduciary duty and related claims in connection with the Offering and formation transactions and seeks monetary damages and declaratory relief. These investors had opted out of a prior class action bringing similar claims that was settled with court approval. The respondents filed an answer and counterclaims. In March 2015, the federal court action was stayed on consent of all parties pending the arbitration. Arbitration hearings for a select number of sessions started in May 2016 and are now scheduled through August 2018. The respondents believe the allegations in the arbitration are entirely without merit, and they intend to continue to defend them vigorously. Pursuant to indemnification agreements which were made with our directors, executive officers and chairman emeritus as part of our formation transactions, Anthony E. Malkin, Peter L. Malkin and Thomas N. Keltner, Jr. have defense and indemnity rights from us with respect to this arbitration. Unfunded Capital Expenditures At March 31, 2018 , we estimate that we will incur approximately $88.0 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 March 31, 2018 were as follows (amounts in thousands): 2018 $ 1,138 2019 1,518 2020 1,518 2021 1,518 2022 1,518 Thereafter 53,694 $ 60,904 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 March 31, 2018 , 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 March 31, 2018 , 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 March 31, 2018 , 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.

Equity

Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Equity	Equity Shares and Units An operating partnership unit of the Operating Partnership ("OP Unit") and a share of our common stock have essentially the same economic characteristics as they receive the same per unit profit distributions of the Operating Partnership. On the one -year anniversary of issuance, an OP Unit may be tendered for redemption for cash; however, we have sole and absolute discretion, and sufficient authorized common stock, to exchange OP Units for shares of common stock on a one-for-one basis instead of cash. Long-term incentive plan ("LTIP") units are a special class of partnership interests in the Operating Partnership. Each LTIP unit awarded will be deemed equivalent to an award of one share of 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, the Operating Partnership 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 OP unitholders. Subject to any agreed upon exceptions, once vested and having achieved parity with OP unitholders, LTIP units are convertible into OP Units in the Operating Partnership on a one-for-one basis. LTIP units subject to time based vesting, whether vested or not, receive the same per unit distributions as OP units, which equal per share dividends (both regular and special) on our common stock. Performance based LTIP units 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. The following is net income attributable to common stockholders and the issuance of our Class A shares in exchange for the conversion of OP Units into common stock (amounts in thousands): Three Months Ended March 31, 2018 March 31, 2017 Net income attributable to common stockholders $ 9,768 $ 9,985 Increase in additional paid-in capital for the conversion of OP Units into common stock 10,162 7,811 Change from net income attributable to common stockholders and transfers from non-controlling interests $ 19,930 $ 17,796 As of March 31, 2018 , there were 302,996,359 OP Units outstanding, of which 164,369,210 , or 54.2% , were owned by us and 138,627,149 , or 45.8% , were owned by other partners, including certain directors, officers and other members of executive management. Dividends and Distributions Total dividends paid to common stockholders were $17.2 million and $16.5 million for the three months ended March 31, 2018 and 2017, respectively. Total distributions paid to OP unitholders, excluding inter-company distributions, were $14.4 million and $14.9 million for the three months ended March 31, 2018 and 2017, respectively. Total distributions paid to preferred unitholders were $0.2 million and $0.2 million for the three months ended March 31, 2018 and 2017, 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 our common stock is authorized for issuance under awards granted pursuant to the 2013 Plan, and as of March 31, 2018 , 4.4 million shares of common stock remain available for future issuance. In March 2018, we made grants of LTIP units to executive officers under the 2013 Plan. At such time, we granted to executive officers a total of 386,876 LTIP units that are subject to time-based vesting and 1,737,917 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 2018, 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 67,449 LTIP units and 39,608 shares of restricted stock that are subject to time-based vesting and 223,950 LTIP units that are subject to performance-based vesting, with fair market values of $1.7 million for the time-based vesting awards and $1.1 million for the performance-based vesting awards. The awards subject to time-based vesting vest ratably over four years from January 1, 2018, subject generally to the grantee's continued employment. The first installment vests on January 1, 2019 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, 2018. 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, 2021 and the second installment vesting on January 1, 2022, subject generally to the grantee's continued employment on those dates. In 2017, our board of directors determined to reinforce the alignment of our executive officers’ interests with that of stockholders by designing a new bonus election program, under which named executive officers could elect to receive their annual incentive bonus in any combination of (i) cash or vested LTIP's at the face amount of such bonus or (ii) time-vesting LTIP's which would vest over three years, subject to continued employment, at 125% of such face amount. In February 2018, we made grants of LTIP units to executive officers under the 2013 Plan in connection with the 2017 bonus election program. We granted to executive officers a total of 238,609 LTIP units that are subject to time based vesting with a fair market value of $4.0 million . Of these LTIP units, 25,158 LTIP units vested immediately on the grant date and 213,451 LTIP units vest ratably over three years from January 1, 2018, subject generally to the grantee's continued employment. The first installment vests on January 1, 2019 and the remainder will vest thereafter in two equal annual installments. 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 restricted stock issued during the three months ended March 31, 2018 were valued at $22.6 million . The weighted-average per unit or share fair value was $8.38 for grants issued in 2018. The per unit or share granted in 2018 was estimated on the respective dates of grant using the following assumptions: an expected life of 5.6 years, a dividend rate of 2.30% , a risk-free interest rate of 2.50% , and an expected price volatility of 17.0% . No other stock options, dividend equivalents, or stock appreciation rights were issued or outstanding in 2018. The following is a summary of restricted stock and LTIP unit activity for the three months ended March 31, 2018 : Restricted Stock LTIP Units Weighted Average Grant Fair Value Unvested balance at December 31, 2017 90,791 3,588,609 $ 11.20 Vested (28,123 ) (437,558 ) 14.19 Granted 39,608 2,654,801 8.38 Forfeited or unearned (6,101 ) (94,173 ) 8.39 Unvested balance at March 31, 2018 96,175 5,711,679 $ 9.70 The LTIP unit and 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 $1.2 million and $0.6 million for the three months ended March 31, 2018 and 2017, respectively. Unrecognized compensation expense was $1.3 million at March 31, 2018 , which will be recognized over a weighted average period of 2.6 years. For the remainder of the LTIP unit and restricted stock awards, we recognize noncash compensation expense ratably over the vesting period, and accordingly, we recognized noncash compensation expense of $3.4 million and $2.6 million for the three months ended March 31, 2018 and 2017, respectively. Unrecognized compensation expense was $40.5 million at March 31, 2018 , which will be recognized over a weighted average period of 2.7 years. Earnings Per Share Earnings per share for the three months ended March 31, 2018 and 2017 is computed as follows (amounts in thousands, except per share amounts): Three Months Ended, March 31, 2018 March 31, 2017 Numerator - Basic: Net income $ 18,058 $ 19,145 Private perpetual preferred unit distributions (234 ) (234 ) Net income attributable to non-controlling interests (8,056 ) (8,926 ) Earnings allocated to unvested shares (6 ) (7 ) Net income attributable to common stockholders - basic $ 9,762 $ 9,978 Numerator - Diluted: Net income $ 18,058 $ 19,145 Private perpetual preferred unit distributions (234 ) (234 ) Earnings allocated to unvested shares (6 ) (7 ) Net income attributable to common stockholders - diluted $ 17,818 $ 18,904 Denominator: Weighted average shares outstanding - basic 162,667 156,493 Operating partnership units 134,157 139,895 Effect of dilutive securities: Stock-based compensation plans 3 775 Exchangeable senior notes — 799 Weighted average shares outstanding - diluted 296,827 297,962 Earnings per share: Basic $ 0.06 $ 0.06 Diluted $ 0.06 $ 0.06 There were 419,347 and 622,565 antidilutive shares and LTIP units for the three months ended March 31, 2018 and 2017.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and 2017, 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 March 31, 2018 and 2017, respectively. These fees are included within third-party management and other fees. Other We receive rent generally at market rental rate for 5,351 square feet of leased space from entities affiliated with Anthony E. Malkin, at one of our properties. Under the lease, the tenant has the right to cancel such lease without special payment on 90 days’ notice. We also 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 $0.1 million for the three months ended March 31, 2018 and, 2017, respectively. One of our 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 $4.0 million as of March 31, 2018 .

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2018
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 months ended March 31, 2018 and 2017 (amounts in thousands): Three Months Ended March 31, 2018 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 122,311 $ — $ — $ 122,311 Intercompany rental revenue 13,561 — (13,561 ) — Tenant expense reimbursement 17,794 — — 17,794 Observatory revenue — 21,249 — 21,249 Lease termination fees 622 — — 622 Third-party management and other fees 463 — — 463 Other revenue and fees 6,057 — — 6,057 Total revenues 160,808 21,249 (13,561 ) 168,496 Operating expenses: Property operating expenses 44,185 — — 44,185 Intercompany rent expense — 13,561 (13,561 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 12,628 — — 12,628 Observatory expenses — 7,336 — 7,336 Real estate taxes 26,744 — — 26,744 Depreciation and amortization 39,865 18 — 39,883 Total operating expenses 125,753 20,915 (13,561 ) 133,107 Total operating income 35,055 334 — 35,389 Other expenses: Interest expense (17,591 ) — — (17,591 ) Income before income taxes 17,464 334 — 17,798 Income tax (expense) benefit (307 ) 567 — 260 Net income $ 17,157 $ 901 $ — $ 18,058 Segment assets $ 3,887,337 $ 254,476 $ — $ 4,141,813 Expenditures for segment assets $ 34,797 $ 11,553 $ — $ 46,350 Three Months Ended March 31, 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 117,113 $ — $ — $ 117,113 Intercompany rental revenue 13,378 — (13,378 ) — Tenant expense reimbursement 15,974 — — 15,974 Observatory revenue — 20,940 — 20,940 Lease termination fees 7,938 — — 7,938 Third-party management and other fees 351 — — 351 Other revenue and fees 2,638 — — 2,638 Total revenues 157,392 20,940 (13,378 ) 164,954 Operating expenses: Property operating expenses 42,210 — — 42,210 Intercompany rent expense — 13,378 (13,378 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 11,088 — — 11,088 Observatory expenses — 7,255 — 7,255 Real estate taxes 24,558 — — 24,558 Depreciation and amortization 40,833 13 — 40,846 Total operating expenses 121,020 20,646 (13,378 ) 128,288 Total operating income 36,372 294 — 36,666 Other expenses: Interest expense (17,742 ) — — (17,742 ) Loss from derivative financial instruments (247 ) — — (247 ) Income before income taxes 18,383 294 — 18,677 Income tax (expense) benefit (283 ) 751 — 468 Net income $ 18,100 $ 1,045 $ — $ 19,145 Segment assets $ 3,617,276 $ 248,900 $ — $ 3,866,176 Expenditures for segment assets $ 48,054 $ 6 $ — $ 48,060

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events None.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
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, 2017 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. The Operating Partnership is a variable interest entity of our company, Empire State Realty Trust, Inc. As the Operating Partnership is already consolidated in the financial statements of Empire State Realty Trust, Inc., the identification of this entity as a variable interest entity has no impact on our consolidated financial statements. 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 balances of other revenues and interest expense have been reclassified to separately present lease termination fees and loss on early extinguishment of debt, respectively.
Recently Issued or Adopted Accounting Standards	During January 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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 is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The amendments are applied prospectively on or after the effective date. No disclosures are required at transition. We believe that acquisitions of real estate properties will generally 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 is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. We adopted this standard on January 1, 2018 using a retrospective transition method. The adoption did not have a material impact 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 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. We adopted this standard on January 1, 2018 using a retrospective transition method. The adoption did not have a material impact 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 March 31, 2018 , the remaining contractual payments under our ground lease agreements aggregated $60.9 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 $2.6 million for the year ended December 31, 2017. 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 replaces 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. We adopted this standard on January 1, 2018 and it did not have a material impact on our consolidated financial statements.

Deferred Costs, Acquired Leas21

Deferred Costs, Acquired Lease Intangibles and Goodwill (Tables)	3 Months Ended
	Mar. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Net	Deferred costs, net, consisted of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Leasing costs $ 166,908 $ 164,751 Acquired in-place lease value and deferred leasing costs 227,086 237,364 Acquired above-market leases 63,191 67,415 457,185 469,530 Less: accumulated amortization (209,143 ) (215,102 ) Total deferred costs, net, excluding net deferred financing costs $ 248,042 $ 254,428 Deferred financing costs, net, consisted of the following at March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Financing costs $ 25,587 $ 24,446 Less: accumulated amortization (7,364 ) (7,039 ) Total deferred financing costs, net $ 18,223 $ 17,407
Amortizing Acquired Intangible Assets and Liabilities	Amortizing acquired intangible assets and liabilities consisted of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Acquired below-market ground leases $ 396,916 $ 396,916 Less: accumulated amortization (30,645 ) (28,687 ) Acquired below-market ground leases, net $ 366,271 $ 368,229 March 31, 2018 December 31, 2017 Acquired below-market leases $ (124,615 ) $ (132,026 ) Less: accumulated amortization 62,197 65,979 Acquired below-market leases, net $ (62,418 ) $ (66,047 )

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	Debt consisted of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): Principal Balance As of March 31, 2018 March 31, 2018 December 31, 2017 Stated Effective (1) Maturity (2) Mortgage debt collateralized by: Fixed rate mortgage debt Metro Center $ 93,428 $ 93,948 3.59 % 3.68 % 11/5/2024 10 Union Square 50,000 50,000 3.70 % 3.97 % 4/1/2026 1542 Third Avenue 30,000 30,000 4.29 % 4.54 % 5/1/2027 First Stamford Place (3) 180,000 180,000 4.28 % 4.39 % 7/1/2027 1010 Third Avenue and 77 West 55th Street 39,534 39,710 4.01 % 4.22 % 1/5/2028 10 Bank Street 34,399 34,602 4.23 % 4.35 % 6/1/2032 383 Main Avenue 30,000 30,000 4.44 % 4.55 % 6/30/2032 1333 Broadway 160,000 66,602 4.21 % 4.21 % 2/5/2033 1400 Broadway (first lien mortgage loan) — 66,632 — — — (second lien mortgage loan) — 9,172 — — — 111 West 33rd Street (first lien mortgage loan) — 74,045 — — — (second lien mortgage loan) — 9,369 — — — 1350 Broadway — 37,144 — — — Total mortgage debt 617,361 721,224 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 % 3.96 % 3/27/2025 Series B 125,000 125,000 4.09 % 4.12 % 3/27/2027 Series C 125,000 125,000 4.18 % 4.21 % 3/27/2030 Series D 115,000 115,000 4.08 % 4.11 % 1/22/2028 Series E 160,000 — 4.26 % 4.26 % 3/22/2030 Series F 175,000 — 4.44 % 4.44 % 3/22/2033 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 1,932,361 1,701,224 Unamortized discount, net of unamortized premium (3,651 ) (3,370 ) Deferred financing costs, net (10,430 ) (9,133 ) Total $ 1,918,280 $ 1,688,721 ______________ (1) The effective rate is the yield as of March 31, 2018 , 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 at 4.09% and a $16 million loan bearing interest at 6.25% . (4) At March 31, 2018 , the unsecured revolving credit facility bears a floating rate at 30 day LIBOR plus 1.10% . The rate at March 31, 2018 was 2.98% . (5) The unsecured term loan facility bears a floating rate at 30 day LIBOR plus 1.20% . Pursuant to an interest rate swap agreement, the LIBOR rate is fixed at 2.1485% through maturity. The rate at March 31, 2018 was 3.35% . (6) At March 31, 2018 , we were in compliance with all debt covenants.
Aggregate Required Principal Payments	Aggregate required principal payments at March 31, 2018 are as follows (amounts in thousands): Year Amortization Maturities Total 2018 $ 2,749 $ — $ 2,749 2019 3,790 250,000 253,790 2020 3,938 — 3,938 2021 4,090 — 4,090 2022 5,628 265,000 270,628 Thereafter 41,744 1,355,422 1,397,166 Total $ 61,939 $ 1,870,422 $ 1,932,361
Deferred Financing Costs, Net	Deferred costs, net, consisted of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Leasing costs $ 166,908 $ 164,751 Acquired in-place lease value and deferred leasing costs 227,086 237,364 Acquired above-market leases 63,191 67,415 457,185 469,530 Less: accumulated amortization (209,143 ) (215,102 ) Total deferred costs, net, excluding net deferred financing costs $ 248,042 $ 254,428 Deferred financing costs, net, consisted of the following at March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Financing costs $ 25,587 $ 24,446 Less: accumulated amortization (7,364 ) (7,039 ) Total deferred financing costs, net $ 18,223 $ 17,407

Accounts Payable and Accrued 23

Accounts Payable and Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following as of March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 December 31, 2017 Accrued capital expenditures $ 74,008 $ 71,769 Accounts payable and accrued expenses 28,516 32,509 Interest rate swap agreements liability — 436 Accrued interest payable 3,642 5,687 Due to affiliated companies 664 448 Total accounts payable and accrued expenses $ 106,830 $ 110,849

Financial Instruments and Fai24

Financial Instruments and Fair Values (Tables)	3 Months Ended
	Mar. 31, 2018
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 the agreement and the fair value of our derivative financial instrument as of March 31, 2018 and December 31, 2017 (dollar amounts in thousands): March 31, 2018 December 31, 2017 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 $ 4,103 $ — $ — $ (436 ) $ 4,103 $ — $ — $ (436 )
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 months ended March 31, 2018 and 2017 (amounts in thousands): Three Months Ended Effects of Cash Flow Hedges March 31, 2018 March 31, 2017 Amount of gain (loss) recognized in other comprehensive income (loss) $ 4,180 $ 1,394 Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (599 ) — The table below shows the effect of our derivative financial instruments designated as cash flow hedges on the condensed consolidated statements of income for the three months ended March 31, 2018 and 2017 (amounts in thousands): Three Months Ended Effects of Cash Flow Hedges March 31, 2018 March 31, 2017 Total interest (expense) presented in the condensed consolidated statements of income in which the effects of cash flow hedges are recorded $ (17,591 ) $ (17,742 ) Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense (599 ) —
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 March 31, 2018 and December 31, 2017 (amounts in thousands): March 31, 2018 Estimated Fair Value Carrying Total Level 1 Level 2 Level 3 Interest rate swaps included in prepaid expenses and other assets $ 4,103 $ 4,103 $ — $ 4,103 $ — Interest rate swaps included in accounts payable and accrued expenses — — — — — Mortgage notes payable 610,826 588,596 — — 588,596 Senior unsecured notes - Exchangeable 245,556 257,903 — 257,903 — Senior unsecured notes - Series A, B, C, D, E and F 798,121 791,005 — — 791,005 Unsecured term loan facility 263,777 265,000 — — 265,000 December 31, 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 436 436 — 436 — Mortgage notes payable 717,164 707,300 — — 707,300 Senior unsecured notes - Exchangeable 244,739 275,723 — 275,723 — Senior unsecured notes - Series A, B, C and D 463,156 460,352 — — 460,352 Unsecured term loan facility 263,662 265,000 — — 265,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Aggregate Required Payments on Ground Leases	Aggregate requir ed payments on ground leases at March 31, 2018 were as follows (amounts in thousands): 2018 $ 1,138 2019 1,518 2020 1,518 2021 1,518 2022 1,518 Thereafter 53,694 $ 60,904

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Change in Net Income Attributable to Common Shareholders	The following is net income attributable to common stockholders and the issuance of our Class A shares in exchange for the conversion of OP Units into common stock (amounts in thousands): Three Months Ended March 31, 2018 March 31, 2017 Net income attributable to common stockholders $ 9,768 $ 9,985 Increase in additional paid-in capital for the conversion of OP Units into common stock 10,162 7,811 Change from net income attributable to common stockholders and transfers from non-controlling interests $ 19,930 $ 17,796
Summary of Restricted Stock and Long-Term Incentive Plan Activity	The following is a summary of restricted stock and LTIP unit activity for the three months ended March 31, 2018 : Restricted Stock LTIP Units Weighted Average Grant Fair Value Unvested balance at December 31, 2017 90,791 3,588,609 $ 11.20 Vested (28,123 ) (437,558 ) 14.19 Granted 39,608 2,654,801 8.38 Forfeited or unearned (6,101 ) (94,173 ) 8.39 Unvested balance at March 31, 2018 96,175 5,711,679 $ 9.70
Earnings Per Share	Earnings per share for the three months ended March 31, 2018 and 2017 is computed as follows (amounts in thousands, except per share amounts): Three Months Ended, March 31, 2018 March 31, 2017 Numerator - Basic: Net income $ 18,058 $ 19,145 Private perpetual preferred unit distributions (234 ) (234 ) Net income attributable to non-controlling interests (8,056 ) (8,926 ) Earnings allocated to unvested shares (6 ) (7 ) Net income attributable to common stockholders - basic $ 9,762 $ 9,978 Numerator - Diluted: Net income $ 18,058 $ 19,145 Private perpetual preferred unit distributions (234 ) (234 ) Earnings allocated to unvested shares (6 ) (7 ) Net income attributable to common stockholders - diluted $ 17,818 $ 18,904 Denominator: Weighted average shares outstanding - basic 162,667 156,493 Operating partnership units 134,157 139,895 Effect of dilutive securities: Stock-based compensation plans 3 775 Exchangeable senior notes — 799 Weighted average shares outstanding - diluted 296,827 297,962 Earnings per share: Basic $ 0.06 $ 0.06 Diluted $ 0.06 $ 0.06

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Components of Segment Profit for Each Segment	The following tables provide components of segment profit for each segment for the three months ended March 31, 2018 and 2017 (amounts in thousands): Three Months Ended March 31, 2018 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 122,311 $ — $ — $ 122,311 Intercompany rental revenue 13,561 — (13,561 ) — Tenant expense reimbursement 17,794 — — 17,794 Observatory revenue — 21,249 — 21,249 Lease termination fees 622 — — 622 Third-party management and other fees 463 — — 463 Other revenue and fees 6,057 — — 6,057 Total revenues 160,808 21,249 (13,561 ) 168,496 Operating expenses: Property operating expenses 44,185 — — 44,185 Intercompany rent expense — 13,561 (13,561 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 12,628 — — 12,628 Observatory expenses — 7,336 — 7,336 Real estate taxes 26,744 — — 26,744 Depreciation and amortization 39,865 18 — 39,883 Total operating expenses 125,753 20,915 (13,561 ) 133,107 Total operating income 35,055 334 — 35,389 Other expenses: Interest expense (17,591 ) — — (17,591 ) Income before income taxes 17,464 334 — 17,798 Income tax (expense) benefit (307 ) 567 — 260 Net income $ 17,157 $ 901 $ — $ 18,058 Segment assets $ 3,887,337 $ 254,476 $ — $ 4,141,813 Expenditures for segment assets $ 34,797 $ 11,553 $ — $ 46,350 Three Months Ended March 31, 2017 Real Estate Observatory Intersegment Elimination Total Revenues: Rental revenue $ 117,113 $ — $ — $ 117,113 Intercompany rental revenue 13,378 — (13,378 ) — Tenant expense reimbursement 15,974 — — 15,974 Observatory revenue — 20,940 — 20,940 Lease termination fees 7,938 — — 7,938 Third-party management and other fees 351 — — 351 Other revenue and fees 2,638 — — 2,638 Total revenues 157,392 20,940 (13,378 ) 164,954 Operating expenses: Property operating expenses 42,210 — — 42,210 Intercompany rent expense — 13,378 (13,378 ) — Ground rent expense 2,331 — — 2,331 General and administrative expenses 11,088 — — 11,088 Observatory expenses — 7,255 — 7,255 Real estate taxes 24,558 — — 24,558 Depreciation and amortization 40,833 13 — 40,846 Total operating expenses 121,020 20,646 (13,378 ) 128,288 Total operating income 36,372 294 — 36,666 Other expenses: Interest expense (17,742 ) — — (17,742 ) Loss from derivative financial instruments (247 ) — — (247 ) Income before income taxes 18,383 294 — 18,677 Income tax (expense) benefit (283 ) 751 — 468 Net income $ 18,100 $ 1,045 $ — $ 19,145 Segment assets $ 3,617,276 $ 248,900 $ — $ 3,866,176 Expenditures for segment assets $ 48,054 $ 6 $ — $ 48,060

Description of Business and O28

Description of Business and Organization - Narrative (Details)	3 Months Ended
	Mar. 31, 2018ft²parceloffice_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)	54.20%
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)	205,708
Retail Site | Manhattan
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property (in square feet)	506,352
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	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Line Items]
Capitalized internal leasing costs		$ 2,600
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	$ 60,904

Deferred Costs, Acquired Leas30

Deferred Costs, Acquired Lease Intangibles and Goodwill - Deferred Costs, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Leasing costs	$ 166,908	$ 164,751
Total deferred costs, gross amount	457,185	469,530
Less: accumulated amortization	(209,143)	(215,102)
Total deferred costs, net, excluding net deferred financing costs	248,042	254,428
Acquired in-place lease value and deferred leasing costs
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets	227,086	237,364
Acquired above-market leases
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets	$ 63,191	$ 67,415

Deferred Costs, Acquired Leas31

Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Deferred Costs [Line Items]
Amortization expense related to deferred leasing costs	$ 6,200	$ 6,200
Revenue related to amortization of acquired above- and below-market leases, net	1,168	1,428
Goodwill	491,479		$ 491,479
Observatory
Deferred Costs [Line Items]
Goodwill	227,500
Real estate
Deferred Costs [Line Items]
Goodwill	264,000
Lease agreements
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	3,400	$ 4,400
Unsecured revolving credit facility | Unsecured term loan facility
Deferred Costs [Line Items]
Net deferred financing costs	$ 7,800		$ 8,300

Deferred Costs, Acquired Leas32

Deferred Costs, Acquired Lease Intangibles and Goodwill - Amortizing Acquired Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Acquired below-market ground leases
Acquired below-market ground leases, gross	$ 396,916	$ 396,916
Less: accumulated amortization	(30,645)	(28,687)
Acquired below-market ground leases, net	366,271	368,229
Acquired below-market leases
Acquired below-market leases, gross	(124,615)	(132,026)
Less: accumulated amortization	62,197	65,979
Acquired below-market leases, net	$ (62,418)	$ (66,047)

Debt - Long-Term Debt (Details)

Debt - Long-Term Debt (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Jan. 31, 2018	Dec. 31, 2017	Aug. 31, 2014
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 0		$ 0
Deferred financing costs, net	(18,223,000)		(17,407,000)
Total	610,826,000		717,164,000
Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	617,361,000		721,224,000
Total principal	1,932,361,000		1,701,224,000
Unamortized discount, net of unamortized premium	(3,651,000)		(3,370,000)
Deferred financing costs, net	(10,430,000)		(9,133,000)
Total	1,918,280,000		1,688,721,000
Metro Center | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 93,428,000		93,948,000
Stated Rate (as a percent)	3.59%
Effective Rate (as a percent)	3.68%
10 Union Square | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 50,000,000		50,000,000
Stated Rate (as a percent)	3.70%
Effective Rate (as a percent)	3.97%
1542 Third Avenue | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 30,000,000		30,000,000
Stated Rate (as a percent)	4.29%
Effective Rate (as a percent)	4.54%
First Stamford Place | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 180,000,000		180,000,000
Stated Rate (as a percent)	4.28%
Effective Rate (as a percent)	4.39%
1010 Third Avenue and 77 West 55th Street | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 39,534,000		39,710,000
Stated Rate (as a percent)	4.01%
Effective Rate (as a percent)	4.22%
10 Bank Street | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 34,399,000		34,602,000
Stated Rate (as a percent)	4.23%
Effective Rate (as a percent)	4.35%
383 Main Avenue | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 30,000,000		30,000,000
Stated Rate (as a percent)	4.44%
Effective Rate (as a percent)	4.55%
1333 Broadway | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 160,000,000		66,602,000
Stated Rate (as a percent)	4.21%	4.21%
Effective Rate (as a percent)	4.21%
Face amount		$ 160,000,000
1400 Broadway - First Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 0		66,632,000
Stated Rate (as a percent)	0.00%
Effective Rate (as a percent)	0.00%
1400 Broadway - Second Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 0		9,172,000
Stated Rate (as a percent)	0.00%
Effective Rate (as a percent)	0.00%
111 West 33rd Street - First Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 0		74,045,000
Stated Rate (as a percent)	0.00%
Effective Rate (as a percent)	0.00%
111 West 33rd Street - Second Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 0		9,369,000
Stated Rate (as a percent)	0.00%
Effective Rate (as a percent)	0.00%
1350 Broadway | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 0		37,144,000
Stated Rate (as a percent)	0.00%
Effective Rate (as a percent)	0.00%
Senior unsecured notes - exchangeable | Convertible Debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 250,000,000		250,000,000
Stated Rate (as a percent)	2.63%			2.625%
Effective Rate (as a percent)	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 (as a percent)	3.93%
Effective Rate (as a percent)	3.96%
Senior unsecured notes, Series B | Senior notes
Debt Instrument [Line Items]
Total	$ 125,000,000		125,000,000
Stated Rate (as a percent)	4.09%
Effective Rate (as a percent)	4.12%
Senior unsecured notes, Series C | Senior notes
Debt Instrument [Line Items]
Total	$ 125,000,000		125,000,000
Stated Rate (as a percent)	4.18%
Effective Rate (as a percent)	4.21%
Senior unsecured notes, Series D | Senior notes
Debt Instrument [Line Items]
Total	$ 115,000,000		$ 115,000,000
Stated Rate (as a percent)	4.08%		4.08%
Effective Rate (as a percent)	4.11%
Face amount			$ 115,000,000
Senior unsecured notes, Series E | Senior notes
Debt Instrument [Line Items]
Total	$ 160,000,000		$ 0
Stated Rate (as a percent)	4.26%		4.26%
Effective Rate (as a percent)	4.26%
Face amount			$ 160,000,000
Senior unsecured notes, Series F | Senior notes
Debt Instrument [Line Items]
Total	$ 175,000,000		$ 0
Stated Rate (as a percent)	4.44%		4.44%
Effective Rate (as a percent)	4.44%
Face amount			$ 175,000,000
Unsecured revolving credit facility | Revolving credit facility
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 0		0
Effective Rate (as a percent)	2.98%
Unsecured revolving credit facility | Revolving credit facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.10%
Unsecured term loan facility | Revolving credit facility
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 265,000,000		$ 265,000,000
Stated Rate (as a percent)	3.35%
Fixed pay rate (as a percent)	2.1485%
Unsecured term loan facility | Revolving credit facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.20%
First Stamford Place - First Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Stated Rate (as a percent)	4.09%
Face amount	$ 164,000,000
First Stamford Place - Second Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Stated Rate (as a percent)	6.25%
Face amount	$ 16,000,000

Debt - Mortgage Debt (Details)

Debt - Mortgage Debt (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Repayment of mortgage notes payable		$ 263,863,000	$ 3,167,000
Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt		617,361,000		$ 721,224,000
1333 Broadway | Mortgages
Debt Instrument [Line Items]
Fixed rate mortgage debt		$ 160,000,000		$ 66,602,000
Face amount	$ 160,000,000
Stated rate (as a percent)	4.21%	4.21%
1400 Broadway | Mortgages
Debt Instrument [Line Items]
Repayment of mortgage notes payable	$ 75,800,000

Debt - Aggregate Required Princ

Debt - Aggregate Required Principal Payments (Details) - Mortgages - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortization
2018, amortization	$ 2,749
2019, amortization	3,790
2020, amortization	3,938
2021, amortization	4,090
2022, amortization	5,628
Thereafter, amortization	41,744
Total, amortization	61,939
Maturities
2018, maturities	0
2019, maturities	250,000
2020, maturities	0
2021, maturities	0
2022, maturities	265,000
Thereafter, maturities	1,355,422
Total, maturities	1,870,422
Total long term debt
2,018	2,749
2,019	253,790
2,020	3,938
2,021	4,090
2,022	270,628
Thereafter	1,397,166
Total	$ 1,932,361	$ 1,701,224

Debt - Deferred Financing Costs

Debt - Deferred Financing Costs, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Financing costs	$ 25,587		$ 24,446
Less: accumulated amortization	(7,364)		(7,039)
Total deferred financing costs, net	18,223		17,407
Amortization of deferred financing costs	1,000	$ 1,300
Unsecured term loan facility | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Net deferred financing costs	$ 7,800		$ 8,300

Debt - Unsecured Revolving Cred

Debt - Unsecured Revolving Credit and Term Loan Facility (Details) - Unsecured term loan facility	1 Months Ended
	Aug. 31, 2017USD ($)option
Unsecured Revolving Credit Facility And Term Loan
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
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 1,100,000,000
Number of options to extend maturity | option	2
Extension period	6 months
Term loan facility
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 265,000,000
Minimum | Unsecured 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
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
	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Aug. 31, 2014USD ($)$ / shares
Debt Instrument [Line Items]
Amortization of deferred financing costs	$ 1,000,000	$ 1,300,000
Convertible Debt | Exchangeable Senior Notes due August 15, 2019
Debt Instrument [Line Items]
Face amount			$ 250,000,000
Stated rate (as a percent)	2.63%		2.625%
Debt conversion ratio	0.0518215
Conversion price (in USD per share) | $ / shares			$ 19.30
Debt interest expense	$ 2,400,000	2,400,000
Contractual interest expense	1,600,000	1,600,000
Accretion of debt discount	700,000	700,000
Amortization of deferred financing costs	$ 100,000	$ 100,000

Debt - Senior Unsecured Notes (

Debt - Senior Unsecured Notes (Details) - Senior notes - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Series D, Series E, and Series F Senior Unsecured Notes
Debt Instrument [Line Items]
Face amount		$ 450,000,000
Senior unsecured notes, Series D
Debt Instrument [Line Items]
Face amount		$ 115,000,000
Stated Rate (as a percent)	4.08%	4.08%
Senior unsecured notes, Series E
Debt Instrument [Line Items]
Face amount		$ 160,000,000
Stated Rate (as a percent)	4.26%	4.26%
Senior unsecured notes, Series F
Debt Instrument [Line Items]
Face amount		$ 175,000,000
Stated Rate (as a percent)	4.44%	4.44%

Accounts Payable and Accrued 40

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued capital expenditures	$ 74,008	$ 71,769
Accounts payable and accrued expenses	28,516	32,509
Interest rate swap agreements liability	0	436
Accrued interest payable	3,642	5,687
Due to affiliated companies	664	448
Total accounts payable and accrued expenses	$ 106,830	$ 110,849

Financial Instruments and Fai41

Financial Instruments and Fair Values - Narrative (Details)	3 Months Ended
	Mar. 31, 2018USD ($)derivative	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 0		$ 436,000
Unrealized gain on valuation of interest rate swap agreements	4,180,000	$ 1,394,000
Loss from derivative financial instruments	0	247,000
Designated as Hedging Instrument | Cash Flow Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred losses on terminated hedges	14,800,000		$ 15,100,000
Loss expected to be reclassified within twelve months	$ 1,500,000
Loss from derivative financial instruments		200,000
Notional amount, terminated		20,000,000
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, number of instruments held | derivative	1		1
Notional amount	$ 265,000,000		$ 265,000,000
Unrealized gain on valuation of interest rate swap agreements	4,800,000	$ 1,400,000
Amount expected to be reclassified within twelve months	40,000
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	$ 4,100,000
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			$ 400,000

Financial Instruments and Fai42

Financial Instruments and Fair Values - Summary of the Terms of Agreements and the Fair Value of Derivative Financial Instruments (Details) - Designated as Hedging Instrument - Cash Flow Hedging - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Asset	$ 4,103,000	$ 0
Liability	0	(436,000)
LIBOR | Interest Rate Swap, One Month LIBOR, 2.1485%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 265,000,000
Pay Rate (as a percent)	2.1485%
Asset	$ 4,103,000	0
Liability	$ 0	$ (436,000)

Financial Instruments and Fai43

Financial Instruments and Fair Values - Effect of Derivative Financial Instruments Designated as Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ (17,591)	$ (17,742)
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income (loss)	4,180	1,394
Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense	(599)	0
Reclassification out of Accumulated Other Comprehensive Income | Accumulated net gain (loss) from cash flow hedges | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ (599)	$ 0

Financial Instruments and Fai44

Financial Instruments and Fair Values - Summary of the Carrying and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in accounts payable and accrued expenses	$ 0	$ 436
Carrying Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	610,826	717,164
Carrying Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	245,556	244,739
Carrying Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	798,121
Carrying Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		463,156
Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	588,596	707,300
Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	257,903	275,723
Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	791,005
Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		460,352
Level 1 | Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 1 | Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 1 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0
Level 1 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		0
Level 2 | Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 2 | Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	257,903	275,723
Level 2 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0
Level 2 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		0
Level 3 | Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	588,596	707,300
Level 3 | Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 3 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	791,005
Level 3 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		460,352
Unsecured term loan facility | Carrying Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	263,777	263,662
Unsecured term loan facility | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Unsecured term loan facility | Level 1 | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Unsecured term loan facility | Level 2 | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Unsecured term loan facility | Level 3 | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
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	4,103	0
Interest rate swaps included in accounts payable and accrued expenses	0	436
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	4,103	0
Interest rate swaps included in accounts payable and accrued expenses	0	436
Interest Rate Swap | 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 | 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	4,103	0
Interest rate swaps included in accounts payable and accrued expenses	0	436
Interest Rate Swap | 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)	3 Months Ended
	Mar. 31, 2018
Minimum
Operating Leases [Line Items]
Term of lease	1 year
Maximum
Operating Leases [Line Items]
Term of lease	21 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 Contingencies47

Commitments and Contingencies - Unfunded Capital Expenditures (Details) $ in Millions	Mar. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Unfunded capital expenditures	$ 88

Commitments and Contingencies48

Commitments and Contingencies - Aggregate Required Payments on Ground Leases (Details) - Ground leases $ in Thousands	Mar. 31, 2018USD ($)
Operating Leased Assets [Line Items]
2,018	$ 1,138
2,019	1,518
2,020	1,518
2,021	1,518
2,022	1,518
Thereafter	53,694
Aggregate required payments on ground leases	$ 60,904

Equity - Shares and Units (Deta

Equity - Shares and Units (Details)	3 Months Ended
	Mar. 31, 2018shares
Equity [Abstract]
OP Unit, redemption term for cash	1 year
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%
OP units outstanding (in shares)	302,996,359
OP units owned by the Company (in shares)	164,369,210
OP units owned by the Company (as a percent)	54.20%
OP units not owned by the Company (in shares)	138,627,149
OP units not owned by the Company (as a percent)	45.80%

Equity - Change in Net Income A

Equity - Change in Net Income Attributable to Common Shareholders (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class of Stock [Line Items]
Net income attributable to common stockholders	$ 9,768	$ 9,985
Increase in additional paid-in capital for the conversion of OP Units into common stock	0
Change from net income attributable to common stockholders and transfers from non-controlling interests	19,930	17,796
Additional Paid-In Capital
Class of Stock [Line Items]
Increase in additional paid-in capital for the conversion of OP Units into common stock	$ 10,162	$ 7,811

Equity - Dividends and Distribu

Equity - Dividends and Distributions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Dividends paid to common shareholders	$ 17,200	$ 16,500
Distributions paid to OP unitholders	14,400	14,900
Private perpetual preferred unit distributions	$ 234	$ 234

Equity - Incentive and Share-Ba

Equity - Incentive and Share-Based Compensation (Details) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)vesting_installmentshares	Feb. 28, 2018USD ($)vesting_installmentshares	Mar. 31, 2018USD ($)$ / sharesshares	Mar. 31, 2017USD ($)	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility rate look-back period			6 years
Weighted-average per unit or share fair value (in USD per share) | $ / shares			$ 8.38
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
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under the plan (in shares)	12,200,000		12,200,000
Number of shares that remain available for future issuance (in shares)	4,400,000		4,400,000
Long-Term Incentive Plan Unit and Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of share-based awards granted in period | $			$ 22.6
Weighted-average per unit or share fair value (in USD per share) | $ / shares			$ 8.38
Expected term			5 years 6 months 24 days
Dividend rate (as a percent)			2.30%
Risk-free interest rate (as a percent)			2.50%
Expected price volatility (as a percent)			17.00%
Long-Term Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			2,654,801
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			39,608
2013 Plan Units, granted in March 2018 | Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	67,449
Fair value of share-based awards granted in period | $	$ 1.7
Award vesting period	4 years
Number of vesting installments | vesting_installment	3
2013 Plan Units, granted in March 2018 | Performance Based Long-Term Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	223,950
Fair value of share-based awards granted in period | $	$ 1.1
Award vesting period	3 years
Number of vesting installments | vesting_installment	2
2013 Plan Units, granted in March 2018 | Time Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	39,608
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 | $			$ 1.2	$ 0.6
Unrecognized compensation expense | $	$ 1.3		$ 1.3
Unrecognized compensation expense, period for recognition			2 years 7 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 | $			$ 3.4	$ 2.6
Unrecognized compensation expense | $	$ 40.5		$ 40.5
Unrecognized compensation expense, period for recognition			2 years 8 months 12 days
Executive Officer | 2013 Plan Units, granted in March 2018 | Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	386,876
Fair value of share-based awards granted in period | $	$ 6.1
Executive Officer | 2013 Plan Units, granted in March 2018 | Performance Based Long-Term Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,737,917
Fair value of share-based awards granted in period | $	$ 9.6
Executive Officer | 2013 Plan Units, granted in February 2018 | Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		238,609
Fair value of share-based awards granted in period | $		$ 4
Award vesting period					3 years
Vesting percentage of award face amount					125.00%
Executive Officer | Vest immediately | Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		25,158
Executive Officer | Vest ratably over three years | Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		213,451
Award vesting period		3 years
Executive Officer | Vest in two equal annual installments | Time Based Long-Tern Incentive Plan Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of vesting installments | vesting_installment		2

Equity - Summary of Restricted

Equity - Summary of Restricted Stock and LTIP Unit Activity (Details)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Weighted Average Grant Fair Value [Roll Forward]
Beginning balance, Unvested, Weighted Average Grant Fair Value (in USD per share) | $ / shares	$ 11.20
Vested, Weighted Average Grant Fair Value (in USD per share) | $ / shares	14.19
Granted, Weighted Average Grant Fair Value (in USD per share) | $ / shares	8.38
Forfeited or unearned, Weighted Average Grant Fair Value (in USD per share) | $ / shares	8.39
Ending balance, Unvested, Weighted Average Grant Fair Value (in USD per share) | $ / shares	$ 9.70
Restricted Stock
Restricted Stock and LTIP Unit Activity [Roll Forward]
Beginning balance, Unvested (in shares)	90,791
Vested (in shares)	(28,123)
Granted (in shares)	39,608
Forfeited or unearned (in shares)	(6,101)
Ending balance, Unvested (in shares)	96,175
Long-Term Incentive Plan Unit
Restricted Stock and LTIP Unit Activity [Roll Forward]
Beginning balance, Unvested (in shares)	3,588,609
Vested (in shares)	(437,558)
Granted (in shares)	2,654,801
Forfeited or unearned (in shares)	(94,173)
Ending balance, Unvested (in shares)	5,711,679

Equity - Earnings Per Share (De

Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator - Basic:
Net income	$ 18,058	$ 19,145
Private perpetual preferred unit distributions	(234)	(234)
Net income attributable to non-controlling interests	(8,056)	(8,926)
Earnings allocated to unvested shares	(6)	(7)
Net income attributable to common stockholders - basic	9,762	9,978
Numerator - Diluted:
Net income	18,058	19,145
Private perpetual preferred unit distributions	(234)	(234)
Earnings allocated to unvested shares	(6)	(7)
Net income attributable to common stockholders - diluted	$ 17,818	$ 18,904
Denominator:
Weighted average shares outstanding - basic (in shares)	162,667,000	156,493,000
Operating partnership units (in shares)	134,157,000	139,895,000
Effect of dilutive securities:
Stock-based compensation plans (in shares)	3,000	775,000
Exchangeable senior notes (in shares)	0	799,000
Weighted average shares outstanding - diluted (in shares)	296,827,000	297,962,000
Earnings per share:
Basic (in USD per share)	$ 0.06	$ 0.06
Diluted (in USD per share)	$ 0.06	$ 0.06
Antidilutive securities (in shares)	419,347	622,565

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)ft²propertydirector	Mar. 31, 2017USD ($)
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | ft²	10,100,000
Number of directors | director	1
Affiliated entities | Supervisory fee revenue
Related Party Transaction [Line Items]
Revenue from related parties	$ 0.3	$ 0.3
Affiliated entities | Property management fee revenue
Related Party Transaction [Line Items]
Revenue from related parties	0.1	0.1
Affiliated entities | Leased space rental
Related Party Transaction [Line Items]
Revenue from related parties	$ 0.1	$ 0.1
Number of properties | property	1
Notice period for lease cancellation	90 days
Affiliated entities | Annualized rent revenue
Related Party Transaction [Line Items]
Revenue from related parties	$ 4
Undivided interest
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | ft²	5,351
Chairman emeritus | Leased space rental
Related Party Transaction [Line Items]
Percentage of lease space occupied by Chairman emeritus and employee (as a percent)	15.00%

Segment Reporting - Narrative (

Segment Reporting - Narrative (Details)	3 Months Ended
	Mar. 31, 2018segment
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
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues:
Rental revenue	$ 122,311	$ 117,113
Intercompany rental revenue	0	0
Tenant expense reimbursement	17,794	15,974
Observatory revenue	21,249	20,940
Lease termination fees	622	7,938
Third-party management and other fees	463	351
Other revenue and fees	6,057	2,638
Total revenues	168,496	164,954
Operating expenses:
Property operating expenses	44,185	42,210
Intercompany rent expense	0	0
Ground rent expenses	2,331	2,331
General and administrative expenses	12,628	11,088
Observatory expenses	7,336	7,255
Real estate taxes	26,744	24,558
Depreciation and amortization	39,883	40,846
Total operating expenses	133,107	128,288
Total operating income	35,389	36,666
Other expenses:
Interest expense	(17,591)	(17,742)
Loss from derivative financial instruments	0	(247)
Income before income taxes	17,798	18,677
Income tax (expense) benefit	260	468
Net income	18,058	19,145
Segment assets	4,141,813	3,866,176	$ 3,931,347
Expenditures for segment assets	46,350	48,060
Intersegment Elimination
Revenues:
Rental revenue	0	0
Intercompany rental revenue	(13,561)	(13,378)
Tenant expense reimbursement	0	0
Observatory revenue	0	0
Lease termination fees	0	0
Third-party management and other fees	0	0
Other revenue and fees	0	0
Total revenues	(13,561)	(13,378)
Operating expenses:
Property operating expenses	0	0
Intercompany rent expense	(13,561)	(13,378)
Ground rent expenses	0	0
General and administrative expenses	0	0
Observatory expenses	0	0
Real estate taxes	0	0
Depreciation and amortization	0	0
Total operating expenses	(13,561)	(13,378)
Total operating income	0	0
Other expenses:
Interest expense	0	0
Loss from derivative financial instruments		0
Income before income taxes	0	0
Income tax (expense) benefit	0	0
Net income	0	0
Segment assets	0	0
Expenditures for segment assets	0	0
Real Estate | Operating Segments
Revenues:
Rental revenue	122,311	117,113
Intercompany rental revenue	13,561	13,378
Tenant expense reimbursement	17,794	15,974
Observatory revenue	0	0
Lease termination fees	622	7,938
Third-party management and other fees	463	351
Other revenue and fees	6,057	2,638
Total revenues	160,808	157,392
Operating expenses:
Property operating expenses	44,185	42,210
Intercompany rent expense	0	0
Ground rent expenses	2,331	2,331
General and administrative expenses	12,628	11,088
Observatory expenses	0	0
Real estate taxes	26,744	24,558
Depreciation and amortization	39,865	40,833
Total operating expenses	125,753	121,020
Total operating income	35,055	36,372
Other expenses:
Interest expense	(17,591)	(17,742)
Loss from derivative financial instruments		(247)
Income before income taxes	17,464	18,383
Income tax (expense) benefit	(307)	(283)
Net income	17,157	18,100
Segment assets	3,887,337	3,617,276
Expenditures for segment assets	34,797	48,054
Observatory | Operating Segments
Revenues:
Rental revenue	0	0
Intercompany rental revenue	0	0
Tenant expense reimbursement	0	0
Observatory revenue	21,249	20,940
Lease termination fees	0	0
Third-party management and other fees	0	0
Other revenue and fees	0	0
Total revenues	21,249	20,940
Operating expenses:
Property operating expenses	0	0
Intercompany rent expense	13,561	13,378
Ground rent expenses	0	0
General and administrative expenses	0	0
Observatory expenses	7,336	7,255
Real estate taxes	0	0
Depreciation and amortization	18	13
Total operating expenses	20,915	20,646
Total operating income	334	294
Other expenses:
Interest expense	0	0
Loss from derivative financial instruments		0
Income before income taxes	334	294
Income tax (expense) benefit	567	751
Net income	901	1,045
Segment assets	254,476	248,900
Expenditures for segment assets	$ 11,553	$ 6