Consolidated Statement of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid- In-Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Noncontrolling Interests	Series I Preferred Stock Preferred Stock
Beginning Balance at Dec. 31, 2014	$ 7,459,216	$ 974	$ 5,113,759	$ 0	$ (6,980)	$ 1,607,689	$ 521,842	$ 221,932
Beginning Balance (in shares) at Dec. 31, 2014		97,325
Increase (Decrease) in Stockholders' Equity
Net income (loss)	299,927					284,084	15,843
Acquisition of subsidiary interest from noncontrolling interest	(20,650)		(9,566)				(11,084)
Other comprehensive income	(1,769)				(1,769)
Preferred dividends	(14,952)					(14,952)
DRSPP (in shares)		776
DRSPP proceeds	99,555	$ 8	99,547
Conversion of units of the Operating Partnership to common stock (in shares)		483
Redemption of units in the operating partnership	55,697	$ 5	55,692
Reallocation of noncontrolling interest in the Operating Partnership	20,915					20,915
Deferred compensation plan and stock award, net (in shares)		168
Deferred compensation plan and stock award, net	(2,982)	$ 2	243			(3,227)
Reallocation of capital account relating to sale	(10,143)						(10,143)
Amortization of deferred compensation plan	26,721		26,721
Issuance of common stock (in shares)		1,007
Issuance of common stock	126,989	$ 10	136,979	(10,000)
Proceeds from stock options exercised (in shares)		217
Proceeds from stock options exercised	16,362	$ 2	16,360
Contributions to consolidated joint venture interests	35,178						35,178
Cash distributions to noncontrolling interests	(119,784)						(119,784)
Cash distributions declared ($2.52, $2.10, and $1.49 per common share, respectively, none of which represented a return of capital for federal income tax purposes)	(250,963)					(250,963)
Ending Balance at Dec. 31, 2015	7,719,317	$ 1,001	5,439,735	(10,000)	(8,749)	1,643,546	431,852	221,932
Ending Balance (in shares) at Dec. 31, 2015		99,976
Increase (Decrease) in Stockholders' Equity
Net income (loss)	257,540					249,896	7,644
Other comprehensive income	30,886				30,886
Preferred dividends	(14,950)					(14,950)
DRSPP (in shares)		2
DRSPP proceeds	277		277
Conversion of units of the Operating Partnership to common stock (in shares)		295
Redemption of units in the operating partnership	31,806	$ 3	31,803
Reallocation of noncontrolling interest in the Operating Partnership	(4,222)					(4,222)
Deferred compensation plan and stock award, net (in shares)		96
Deferred compensation plan and stock award, net	(1,988)	$ 1	(1,989)
Amortization of deferred compensation plan	25,890		25,890
Issuance of common stock (in shares)
Issuance of common stock	(40)	$ 10	113,999	(114,049)
Proceeds from stock options exercised (in shares)		193
Proceeds from stock options exercised	14,832	$ 2	14,830
Contributions to consolidated joint venture interests	2,359						2,359
Cash distributions to noncontrolling interests	(15,419)						(15,419)
Cash distributions declared ($2.52, $2.10, and $1.49 per common share, respectively, none of which represented a return of capital for federal income tax purposes)	(295,377)					(295,377)
Ending Balance at Dec. 31, 2016	7,750,911	$ 1,017	5,624,545	(124,049)	22,137	1,578,893	426,436	221,932
Ending Balance (in shares) at Dec. 31, 2016		100,562
Increase (Decrease) in Stockholders' Equity
Net income (loss)	85,673					101,374	(15,701)
Other comprehensive income	(3,533)				(3,533)
Preferred dividends	(14,950)					(14,950)
DRSPP (in shares)		2
DRSPP proceeds	223		223
Conversion of units of the Operating Partnership to common stock (in shares)		202
Redemption of units in the operating partnership	21,574	$ 2	21,572
Reallocation of noncontrolling interest in the Operating Partnership	5,712					5,712
Equity component of repurchased exchangeable senior notes	(109,776)		(109,776)
Deferred compensation plan and stock award, net (in shares)		87
Deferred compensation plan and stock award, net	(2,374)	$ 1	(2,375)
Amortization of deferred compensation plan	32,161		32,161
Repurchases of common stock (in shares)		(8,342)
Repurchases of common stock	(848,048)	$ (83)	(621,324)			(226,641)
Proceeds from stock options exercised (in shares)		292
Proceeds from stock options exercised	23,314	$ 2	23,312
Contributions to consolidated joint venture interests	36,275						36,275
Deconsolidation of partially owned entity	(30,203)						(30,203)
Cash distributions to noncontrolling interests	(52,446)						(52,446)
Cash distributions declared ($2.52, $2.10, and $1.49 per common share, respectively, none of which represented a return of capital for federal income tax purposes)	(305,059)					(305,059)
Ending Balance at Dec. 31, 2017	$ 6,589,454	$ 939	$ 4,968,338	$ (124,049)	$ 18,604	$ 1,139,329	$ 364,361	$ 221,932
Ending Balance (in shares) at Dec. 31, 2017		92,803