CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Earnings Less than Distributions [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member] Consolidated Joint Ventures [Member]	Noncontrolling Interest [Member] Consolidated Real Estate Funds [Member]	Noncontrolling Interest [Member] Operating Partnership [Member]
Beginning balance (Scenario, Previously Reported) at Dec. 31, 2015	$ 5,310,550	$ 2,122	$ 3,802,858	$ (36,120)	$ (7,843)	$ 236,849	$ 414,637	$ 898,047
Beginning balance (Scenario, Adjustment, Deconsolidation of real estate fund investments upon adoption of ASU 2015-02) at Dec. 31, 2015	(351,035)						(351,035)
Beginning balance at Dec. 31, 2015	4,959,515	$ 2,122	3,802,858	(36,120)	(7,843)	236,849	63,602	898,047
Common stock, shares outstanding (Scenario, Previously Reported) at Dec. 31, 2015		212,112,000
Common stock, shares outstanding at Dec. 31, 2015		212,112,000
Net income (loss)	4,892			(3,445)		10,062	(819)	(906)
Common shares issued upon redemption of common units		$ 74	126,068
Common shares issued upon redemption of common units		7,403,000
Redemption of minority interest in operating partnerships								(126,142)
Common shares issued under Omnibus share plan, net of shares withheld for taxes		97,000
Dividends and distributions ($0.285 per share and unit)	(75,449)			(61,953)				(13,496)
Distributions to noncontrolling interests	(2,692)					(2,692)
Change in value of interest rate swaps	(33,812)				(27,231)			(6,581)
Pro rata share of other comprehensive income (loss) of unconsolidated joint ventures	(19)				(18)			(1)
Amortization of equity awards	9,624		1,605					8,019
Other	231		18	191		15	7
Ending balance at Sep. 30, 2016	4,862,290	$ 2,196	3,930,549	(101,327)	(35,092)	244,234	62,790	758,940
Common stock, shares outstanding at Sep. 30, 2016		219,612,000
Beginning balance at Dec. 31, 2016	$ 4,885,947	$ 2,300	4,116,987	(129,654)	372	253,788	64,793	577,361
Common stock, shares outstanding at Dec. 31, 2016	230,015,356	230,015,000
Net income (loss)	$ 114,408			93,174		(11,029)	20,195	12,068
Common shares issued upon redemption of common units		$ 100	166,424
Common shares issued upon redemption of common units		10,001,000
Redemption of minority interest in operating partnerships								(166,524)
Common shares issued under Omnibus share plan, net of shares withheld for taxes	(154)			(154)
Common shares issued under Omnibus share plan, net of shares withheld for taxes		58,000
Dividends and distributions ($0.285 per share and unit)	(75,629)			(67,425)				(8,204)
Contributions from noncontrolling interests	100,777					96,472	4,305
Distributions to noncontrolling interests	(115,549)					(41,203)	(74,346)
Consolidation of 50 Beale Street	110,007					110,007
Change in value of interest rate swaps	729				600			129
Pro rata share of other comprehensive income (loss) of unconsolidated joint ventures	39				42			(3)
Amortization of equity awards	13,126		2,244					10,882
Other	8,455		610					7,845
Ending balance at Sep. 30, 2017	$ 5,042,156	$ 2,400	$ 4,286,265	$ (104,059)	$ 1,014	$ 408,035	$ 14,947	$ 433,554
Common stock, shares outstanding at Sep. 30, 2017	240,073,742	240,074,000