CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (33,863,000)	$ 139,811,000
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	129,931,000	131,628,000
Real estate impairment loss	46,000,000
Amortization of deferred financing costs	5,515,000	5,548,000
Gain on sale of real estate		(133,989,000)
Straight-lining of rental income	(29,983,000)	(32,121,000)
Amortization of above and below-market leases, net	(8,724,000)	(10,989,000)
Loss on early extinguishment of debt		7,877,000
Unrealized gain on interest rate swaps		(1,802,000)
Realized and unrealized losses (gains) on marketable securities	1,000	(2,486,000)
Income from unconsolidated joint ventures	(2,459,000)	(18,472,000)
Distributions of earnings from unconsolidated joint ventures	1,170,000	2,758,000
Loss from unconsolidated real estate funds	80,000	2,123,000
Distributions of earnings from unconsolidated real estate funds	135,000	146,000
Amortization of stock-based compensation expense	10,915,000	7,867,000
Other non-cash adjustments	40,000	(169,000)
Changes in operating assets and liabilities:
Accounts and other receivables	1,533,000	3,102,000
Deferred charges	(13,734,000)	(14,297,000)
Other assets	(1,910,000)	7,294,000
Accounts payable and accrued expenses	1,297,000	(15,257,000)
Other liabilities	567,000	420,000
Net cash provided by operating activities	106,511,000	78,992,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to real estate	(51,610,000)	(33,079,000)
Investments in unconsolidated joint ventures	(17,137,000)	(28,791,000)
Escrow deposits and loans receivable for Residential Development Fund	(15,680,000)
Sales of marketable securities	15,253,000	9,543,000
Purchases of marketable securities	(12,140,000)	(6,230,000)
Distributions of capital from unconsolidated joint ventures	2,608,000	20,000,000
Contributions of capital to unconsolidated real estate funds	(2,254,000)	(584,000)
Proceeds from sale of real estate		540,333,000
Deposit on real estate		(12,914,000)
Distributions of capital from unconsolidated real estate funds		3,845,000
Net cash (used in) provided by investing activities	(80,960,000)	492,123,000
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends paid to common stockholders	(46,892,000)	(43,832,000)
Contributions from noncontrolling interests	36,128,000	9,278,000
Proceeds from notes and mortgages payable	16,700,000	991,556,000
Debt issuance costs	(6,351,000)	(7,344,000)
Distributions paid to common unitholders	(4,945,000)	(6,526,000)
Distributions to noncontrolling interests	(4,118,000)	(107,162,000)
Repurchase of shares related to stock compensation agreements and related tax withholdings	(213,000)	(154,000)
Repayments of notes and mortgages payable		(1,044,821,000)
Repayment of borrowings under revolving credit facility		(290,000,000)
Borrowings under revolving credit facility		60,000,000
Settlement of interest rate swap liabilities		(19,425,000)
Loss on early extinguishment of debt		(7,877,000)
Net cash used in financing activities	(9,691,000)	(466,307,000)
Net increase in cash and cash equivalents and restricted cash	15,860,000	104,808,000
Cash and cash equivalents and restricted cash at beginning of period	250,425,000	192,339,000
Cash and cash equivalents and restricted cash at end of period	266,285,000	297,147,000
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents at beginning of period	219,381,000	162,965,000
Restricted cash at beginning of period	31,044,000	29,374,000
Cash and cash equivalents and restricted cash at beginning of period	250,425,000	192,339,000
Cash and cash equivalents at end of period	233,530,000	254,763,000
Restricted cash at end of period	32,755,000	42,384,000
Cash and cash equivalents and restricted cash at end of period	266,285,000	297,147,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash payments for interest	67,367,000	73,817,000
Cash payments for income taxes, net of refunds	1,699,000	3,191,000
NON-CASH TRANSACTIONS:
Dividends and distributions declared but not yet paid	26,621,000	25,211,000
Additions to real estate included in accounts payable and accrued expenses	10,400,000	8,988,000
Basis adjustment to investment in unconsolidated joint ventures upon adoption of ASU 2017-05	7,086,000
Write-off of fully amortized and/or depreciated assets	2,947,000	4,930,000
Common shares issued upon redemption of common units	469,000	135,959,000
Increase (decrease) in value of interest rate swaps	$ 20,346,000	(9,000)
Increase (decrease) due to deconsolidation of One Steuart Lane:
Investments in unconsolidated joint ventures		14,915,000
Real estate, net		$ (14,915,000)