CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities:
Net (loss) income	$ (19,196)	$ (29,603)	$ 18,993
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	235,890	248,347	258,225
Straight-lining of rental revenue	(28,216)	(43,679)	(59,061)
Amortization of stock-based compensation expense	19,239	22,860	19,646
Loss (income) from unconsolidated joint ventures	18,619	4,706	(3,468)
Loss (gain) on sale of real estate related to discontinued operations	12,766	(1,140)	(36,845)
Amortization of deferred financing costs	9,277	19,323	11,023
Amortization of above and below-market leases, net	(4,734)	(10,991)	(16,059)
Distributions of earnings from unconsolidated joint ventures	3,999	4,067	6,207
Realized and unrealized (gains) losses on marketable securities	(1,918)	(3,027)	1,604
Distributions of earnings from unconsolidated real estate funds	616	1,553	330
(Income) loss from unconsolidated real estate funds	(272)	343	269
Real estate impairment loss related to discontinued operations		42,000	46,000
Receipt of accrued interest on preferred equity investment		2,339
Loss on early extinguishment of debt		731
Other non-cash adjustments	413	(961)	288
Changes in operating assets and liabilities:
Accounts and other receivables	1,729	845	(2,994)
Deferred charges	(10,761)	(23,029)	(31,861)
Other assets	(2,193)	57,318	(57,216)
Accounts payable and accrued expenses	(1,299)	(8,949)	4,200
Other liabilities	3,313	2,388	(2,758)
Net cash provided by operating activities	237,272	285,441	156,523
Cash Flows from Investing Activities:
Additions to real estate	(89,463)	(103,916)	(137,915)
Proceeds from the sale of real estate related to discontinued operations	89,206	150,307	349,013
Repayment of amounts due from affiliates	36,918	181,000
Sales of marketable securities	22,188	19,282	24,794
Purchases of marketable securities	(15,809)	(15,232)	(20,019)
Contributions of capital to unconsolidated real estate funds	(2,945)	(3,937)	(3,779)
Investments in and contributions of capital to unconsolidated joint ventures	(60)	(368,852)	(29,883)
Due from affiliates		(217,918)
Redemption of preferred equity investment		33,750
Distributions of capital from unconsolidated real estate funds		2,076	79
Escrow deposits and loans receivable for Residential Development Fund			(15,680)
Real estate acquisition deposits			(10,000)
Net cash provided by (used in) investing activities	40,035	(323,440)	156,610
Cash Flows from Financing Activities:
Repayment of borrowings under revolving credit facility	(200,000)	(195,000)
Borrowings under revolving credit facility	163,082	231,918
Repurchases of common shares	(120,000)	(97,137)	(102,863)
Proceeds from the sale of a 10.0% interest in 1633 Broadway	111,984
Dividends paid to common stockholders	(89,225)	(93,038)	(94,991)
Distributions paid to common unitholders	(8,837)	(10,073)	(10,064)
Distributions to noncontrolling interests	(12,717)	(45,239)	(18,184)
Contributions from noncontrolling interests	11,555	14,989	45,116
Proceeds from notes and mortgages payable	9,791	1,259,843	16,700
Repayment of note payable issued in connection with the acquisition of noncontrolling interest in consolidated real estate fund	(8,771)
Repurchase of shares related to stock compensation agreements and related tax withholdings	(332)	(324)
Repayments of notes and mortgages payable		(1,050,000)
Debt issuance costs and other		(10,131)	(6,564)
Acquisition of noncontrolling interest in consolidated real estate fund		(1,000)
Loss on early extinguishment of debt		(731)
Repayment of loans to affiliates			(27,299)
Net cash (used in) provided by financing activities	(143,470)	4,077	(198,149)
Net increase (decrease) in cash and cash equivalents and restricted cash	133,837	(33,922)	114,984
Cash and cash equivalents and restricted cash at beginning of period	331,487	365,409	250,425
Cash and cash equivalents and restricted cash at end of period	465,324	331,487	365,409
Reconciliation of Cash and Cash Equivalents and Restricted Cash:
Cash and cash equivalents at beginning of period	306,215	339,653	219,381
Restricted cash at beginning of period	25,272	25,756	31,044
Cash and cash equivalents and restricted cash at beginning of period	331,487	365,409	250,425
Cash and cash equivalents at end of period	434,530	306,215	339,653
Restricted cash at end of period	30,794	25,272	25,756
Cash and cash equivalents and restricted cash at end of period	465,324	331,487	365,409
Supplemental Disclosure of Cash Flow Information:
Cash payments for interest	135,607	139,130	136,452
Cash payments for income taxes, net of refunds	1,366	2,474	4,049
Non-Cash Transactions:
Common shares issued upon redemption of common units	85,710	24,030	3,461
Dividends and distributions declared but not yet paid	16,796	25,255	25,902
Write-off of fully amortized and/or depreciated assets	9,141	8,727	4,158
Additions to real estate included in accounts payable and accrued expenses	$ 8,640	21,566	19,872
Change in value of interest rate swaps		28,069	(7,273)
Note payable issued in connection with the acquisition of noncontrolling interest in consolidated real estate fund		$ 8,771
Basis adjustment to investment in unconsolidated joint ventures upon adoption of ASU 2017-05			$ 7,086