Consolidated Statement Of Shareholders' Equity - 6 months ended Jun. 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 $1,411 attributable to redeemable noncontrolling interests	136,550				132,896		3,654
Other comprehensive loss - change in value of interest rate swaps	(3,183)					(3,183)
Dividends declared to common shareholders	(133,589)				(133,589)
Dividends declared to preferred shareholders	(271)				(271)
Distributions declared to noncontrolling interests	(4,505)						(4,505)
Common shares issued (in shares)			1,603,685
Common shares issued	240,836		$ 16	240,820
Exercise of stock options (in shares)			50,881
Exercise of stock options	4,175		$ 0	4,175
Shares issued under dividend reinvestment plan (in shares)			8,331
Shares issued under dividend reinvestment plan	1,257			1,257
Share-based compensation expense, net of forfeitures (in shares)			125,484
Share-based compensation expense, net of forfeitures	6,052		$ 2	6,050
Shares withheld for employee taxes (in shares)			(30,160)
Shares withheld for employee taxes	(4,371)			(4,371)
Conversion and redemption of OP units (in shares)			165,640
Conversion and redemption of OP units	0		$ 2	18,162			18,164
Contributions from noncontrolling interests	80						80
Adjustment to redeemable noncontrolling interests	(1,976)			(1,976)
Ending balance (in shares) at Jun. 30, 2016		399,896	71,417,253
Ending balance at Jun. 30, 2016	$ 2,022,986	$ 9,997	$ 716	$ 2,645,984	$ (725,665)	$ (7,293)	$ 99,247