Consolidated Statement Of Shareholders' Equity - 9 months ended Sep. 30, 2015 - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2014		399,896	68,605,783
Beginning balance at Dec. 31, 2014	$ 1,692,556	$ 9,997	$ 687	$ 2,281,223	$ (683,991)	$ (3,515)	$ 88,155
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding $2,622 attributable to redeemable noncontrolling interests	145,804				142,265		3,539
Other comprehensive loss - change in value of interest rate swaps	(3,615)					(3,615)
Dividends declared to common shareholders	(185,071)				(185,071)
Dividends declared to preferred shareholders	(406)				(406)
Distributions declared to noncontrolling interests	(4,043)						(4,043)
Common shares issued (in shares)			750,503
Common shares issued	99,573		$ 8	99,565
Exercise of stock options (in shares)			20,739
Exercise of stock options	1,318		$ 0	1,318
Shares issued under dividend reinvestment plan (in shares)			12,423
Shares issued under dividend reinvestment plan	1,717			1,717
Share-based compensation expense, net of forfeitures (in shares)			54,978
Share-based compensation expense, net of forfeitures	9,451		$ 1	9,450
Shares withheld for employee taxes (in shares)			(35,163)
Shares withheld for employee taxes	(5,082)		$ 0	(5,082)
Conversion and redemption of OP units (in shares)			39,611
Conversion and redemption of OP units	(151)			4,072			(4,223)
Contributions from noncontrolling interests	28,443						28,443
Adjustment to redeemable noncontrolling interests	(2,919)			(2,919)
Ending balance (in shares) at Sep. 30, 2015		399,896	69,448,874
Ending balance at Sep. 30, 2015	$ 1,777,575	$ 9,997	$ 696	$ 2,389,344	$ (727,203)	$ (7,130)	$ 111,871