CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Earnings (Less than) In Excess of Distributions [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interest [Member] Consolidated Real Estate Funds [Member]	Noncontrolling Interest [Member] Consolidated Joint Ventures [Member]	Noncontrolling Interest [Member] Operating Partnership [Member]
Beginning balance at Dec. 31, 2014	$ 5,554,953	$ 2,122	$ 3,851,432	$ 57,308		$ 338,070	$ 347,818	$ 958,203
Common stock, shares outstanding at Dec. 31, 2014		212,107,000
Net (loss) income	(8,279)			(14,440)		8,741	931	(3,511)
Common shares issued under Omnibus share plan		5,000
Common units issued under Omnibus share plan			(2,131)					2,131
Dividends and distributions	(60,392)			(48,573)				(11,819)
Contributions from noncontrolling interests	14,031					11,501	2,530
Distributions to noncontrolling interests	(5,673)					(4,957)	(716)
Pro rata share of other comprehensive income (loss) of unconsolidated joint ventures	(613)				$ (493)			(120)
Adjustments to noncontrolling interests			43,981					(43,981)
Amortization of equity awards	4,665		885					3,780
Other	(871)		(411)	(138)		(322)
Ending balance at Jun. 30, 2015	5,497,821	$ 2,122	3,893,756	(5,843)	(493)	353,033	350,563	904,683
Common stock, shares outstanding at Jun. 30, 2015		212,112,000
Beginning balance at Dec. 31, 2015	$ 5,310,550	$ 2,122	3,802,858	(36,120)	(7,843)	414,637	236,849	898,047
Common stock, shares outstanding at Dec. 31, 2015	212,112,137	212,112,000
Deconsolidation of real estate fund investments at Dec. 31, 2015	$ (351,035)					(351,035)
Beginning balance, after adjustment at Dec. 31, 2015	4,959,515	$ 2,122	3,802,858	(36,120)	(7,843)	63,602	236,849	898,047
Net (loss) income	423			(3,306)		(752)	5,359	(878)
Common shares issued upon redemption of common units		$ 73	124,006					(124,079)
Common shares issued upon redemption of common units		7,277,000
Common shares issued under Omnibus share plan		101,000
Dividends and distributions	(50,298)			(41,090)				(9,208)
Distributions to noncontrolling interests	(1,740)						(1,740)
Change in value of interest rate swaps	(41,614)				(33,705)			(7,909)
Pro rata share of other comprehensive income (loss) of unconsolidated joint ventures	63				50			13
Amortization of equity awards	6,719		1,175					5,544
Other	(125)		(167)	20		7	15
Ending balance at Jun. 30, 2016	$ 4,872,943	$ 2,195	$ 3,927,872	$ (80,496)	$ (41,498)	$ 62,857	$ 240,483	$ 761,530
Common stock, shares outstanding at Jun. 30, 2016	219,490,007	219,490,000