Consolidated Statement Of Shareholders' Equity (USD $) In Thousands, except Share data	Total	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Dividends in Excess of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Beginning balance at Dec. 31, 2010	$ 1,115,768	$ 9,997	$ 615	$ 1,611,706	$ (527,582)	$ 0	$ 21,032
Beginning balance (in shares) at Dec. 31, 2010		399,896	61,526,418
Net income	146,120				143,917		2,203
Other Comprehensive Income (Loss), Net of Tax	(3,940)					(3,940)
Dividends declared to common shareholders	(171,335)				(171,335)
Dividends declared to preferred shareholders	(541)				(541)
Distributions declared to noncontrolling interests	(2,320)						(2,320)
Common shares issued (in shares)			1,662,230
Common shares issued	139,298		17	139,281
Exercise of stock options (in shares)			237,271
Exercise of stock options	15,190		3	15,187
Shares issued under dividend reinvestment plan (in shares)	28,823		28,823
Shares issued under dividend reinvestment plan	2,374			2,374
Share-based compensation expense, net (in shares)			89,408
Share-based compensation expense, net	8,247		1	8,246
Conversion and redemption of OP units	(151)			(96)			(55)
Purchase of noncontrolling interest	(2,538)			(2,331)			(207)
Deconsolidation of VIE	(420)						(420)
Contributions from noncontrolling interests	4,279						4,279
Adjustment to redeemable noncontrolling interests	(9,427)			(9,427)
Ending balance at Dec. 31, 2011	1,240,604	9,997	636	1,764,940	(555,541)	(3,940)	24,512
Ending balance (in shares) at Dec. 31, 2011		399,896	63,544,150
Net income	153,640				151,925		1,715
Other Comprehensive Income (Loss), Net of Tax	(8,448)					(8,448)
Dividends declared to common shareholders	(182,813)				(182,813)
Dividends declared to preferred shareholders	(541)				(541)
Distributions declared to noncontrolling interests	(2,232)						(2,232)
Common shares issued (in shares)			1,039,405
Common shares issued	106,219		10	106,209
Exercise of stock options (in shares)			97,430
Exercise of stock options	5,667		1	5,666
Shares issued under dividend reinvestment plan (in shares)	22,814		22,814
Shares issued under dividend reinvestment plan	2,248			2,248
Share-based compensation expense, net (in shares)			111,647
Share-based compensation expense, net	10,371		1	10,370
Conversion and redemption of OP units	(828)			(439)			(389)
Contributions from noncontrolling interests	175						175
Adjustment to redeemable noncontrolling interests	(13,469)			(13,469)
Ending balance at Dec. 31, 2012	1,310,593	9,997	648	1,875,525	(586,970)	(12,388)	23,781
Ending balance (in shares) at Dec. 31, 2012		399,896	64,815,446
Net income	164,721				162,681		2,040
Other Comprehensive Income (Loss), Net of Tax	10,971					10,971
Dividends declared to common shareholders	(198,965)				(198,965)
Dividends declared to preferred shareholders	(541)				(541)
Distributions declared to noncontrolling interests	(1,887)						(1,887)
Common shares issued (in shares)			1,735,089
Common shares issued	185,182		18	185,164
Exercise of stock options (in shares)	16,554		16,554
Exercise of stock options	1,015		0	1,015
Shares issued under dividend reinvestment plan (in shares)	20,026		20,026
Shares issued under dividend reinvestment plan	2,130			2,130
Share-based compensation expense, net (in shares)			91,831
Share-based compensation expense, net	9,357		1	9,356
Conversion and redemption of OP units (in shares)			22,476
Conversion and redemption of OP units	(1,422)			(625)			(797)
Adjustment to redeemable noncontrolling interests	(9,857)			(9,857)
Ending balance at Dec. 31, 2013	$ 1,471,297	$ 9,997	$ 667	$ 2,062,708	$ (623,795)	$ (1,417)	$ 23,137
Ending balance (in shares) at Dec. 31, 2013		399,896	66,701,422