CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 114,408,000	$ 4,892,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	198,143,000	208,475,000
Amortization of deferred financing costs	8,367,000	4,121,000
Gain on sale of real estate	(133,989,000)
Straight-lining of rental income	(43,529,000)	(67,843,000)
Amortization of above and below-market leases, net	(14,164,000)	(6,593,000)
Loss on early extinguishment of debt	7,877,000
Unrealized gain on interest rate swaps	(1,802,000)	(29,661,000)
Realized and unrealized gains on marketable securities	(3,198,000)	(341,000)
Valuation allowance on preferred equity investment	19,588,000
Income from unconsolidated joint ventures	(19,143,000)	(5,291,000)
Distributions of earnings from unconsolidated joint ventures	3,380,000	5,824,000
Loss from unconsolidated real estate funds	6,053,000	2,540,000
Distributions of earnings from unconsolidated real estate funds	275,000	308,000
Amortization of stock-based compensation expense	11,692,000	8,766,000
Other non-cash adjustments	395,000	1,981,000
Changes in operating assets and liabilities:
Accounts and other receivables	2,260,000	(1,455,000)
Deferred charges	(25,429,000)	(11,266,000)
Other assets	(18,094,000)	(39,338,000)
Accounts payable and accrued expenses	(10,710,000)	(3,335,000)
Deferred income taxes	(1,499,000)	(2,979,000)
Other liabilities	4,190,000	1,343,000
Net cash provided by operating activities	105,071,000	70,148,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sale of real estate	540,333,000
Acquisitions of real estate	(161,184,000)
Additions to real estate	(59,255,000)	(107,445,000)
Investments in unconsolidated joint ventures	(28,886,000)
Distributions of capital from unconsolidated joint ventures	20,000,000
Deposits on real estate		(50,000,000)
Changes in restricted cash	(8,224,000)	11,380,000
Distributions of capital from unconsolidated real estate funds	13,849,000
Contributions of capital to unconsolidated real estate funds	(790,000)	(1,084,000)
Net cash provided by (used in) investing activities	315,843,000	(147,149,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of notes and mortgages payable	(1,044,821,000)	(414,564,000)
Proceeds from notes and mortgages payable	991,556,000	509,578,000
Repayment of borrowings under revolving credit facility	(290,000,000)	(80,000,000)
Borrowings under revolving credit facility	60,000,000	110,000,000
Distributions to noncontrolling interests	(115,549,000)	(2,692,000)
Contributions from noncontrolling interests	100,777,000
Dividends paid to common stockholders	(66,469,000)	(61,241,000)
Settlement of interest rate swap liabilities	(19,425,000)	(16,040,000)
Loss on early extinguishment of debt	(7,877,000)
Debt issuance costs	(7,344,000)	(6,532,000)
Transfer tax refund in connection with the acquisition of noncontrolling interests	9,555,000
Distributions paid to common unitholders	(9,100,000)	(14,124,000)
Repurchase of shares related to stock compensation agreements and related tax withholdings	(154,000)
Net cash (used in) provided by financing activities	(398,851,000)	24,385,000
Net increase (decrease) in cash and cash equivalents	22,063,000	(52,616,000)
Cash and cash equivalents at beginning of period	162,965,000	143,884,000
Decrease in cash due to deconsolidation of real estate fund investments		(7,987,000)
Cash and cash equivalents at end of period	185,028,000	83,281,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash payments for interest	106,731,000	106,015,000
Cash payments for income taxes, net of refunds	5,042,000	1,524,000
NON-CASH TRANSACTIONS:
Common shares issued upon redemption of common units	166,524,000	126,142,000
Dividends and distributions declared but not yet paid	25,211,000	25,151,000
Write-off of fully amortized and/or depreciated assets	5,958,000	8,475,000
Additions to real estate included in accounts payable and accrued expenses	10,986,000	6,609,000
Purchases of marketable securities resulting in a decrease to restricted cash	2,278,000	139,000
Change in fair value of interest rate swaps	(729,000)	33,812,000
Consolidation (deconsolidation) of real estate and real estate fund investments	102,512,000	$ (396,697,000)
Assumption of notes and mortgages payable	$ 228,000,000