Consolidated Statement Of Shareholders' Equity - 9 months ended Sep. 30, 2016 - 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, 2015		399,896	69,493,392
Beginning balance at Dec. 31, 2015	$ 1,781,931	$ 9,997	$ 696	$ 2,381,867	$ (724,701)	$ (4,110)	$ 118,182
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding $2,133 attributable to redeemable noncontrolling interests	197,026				191,873		5,153
Other comprehensive loss - change in value of interest rate swaps	(1,284)					(1,284)
Dividends declared to common shareholders	(203,890)				(203,890)
Dividends declared to preferred shareholders	(406)				(406)
Distributions declared to noncontrolling interests	(6,433)						(6,433)
Common shares issued (in shares)			1,950,253
Common shares issued	295,472		$ 20	295,452
Exercise of stock options (in shares)			52,365
Exercise of stock options	4,285		$ 1	4,284
Shares issued under dividend reinvestment plan (in shares)			11,644
Shares issued under dividend reinvestment plan	1,806			1,806
Share-based compensation expense, net of forfeitures (in shares)			135,289
Share-based compensation expense, net of forfeitures	8,818		$ 2	8,816
Shares withheld for employee taxes (in shares)			(30,562)
Shares withheld for employee taxes	(4,436)			(4,436)
Conversion and redemption of OP units (in shares)			170,608
Conversion and redemption of OP units	0		$ 2	18,677			18,679
Contributions from noncontrolling interests	302						302
Adjustment to redeemable noncontrolling interests	(1,976)			(1,976)
Ending balance (in shares) at Sep. 30, 2016		399,896	71,782,989
Ending balance at Sep. 30, 2016	$ 2,071,215	$ 9,997	$ 721	$ 2,704,490	$ (737,124)	$ (5,394)	$ 98,525