Consolidated Statement Of Shareholders' Equity - 9 months ended Sep. 30, 2017 - 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	Preferred Shares Additional Paid-in Capital	Common Shares	Common Shares Additional Paid-in Capital
Beginning balance (in shares) at Dec. 31, 2016		399,896	71,995,897
Beginning balance at Dec. 31, 2016	$ 2,075,835	$ 9,997	$ 722	$ 2,718,325	$ (749,734)	$ (2,577)	$ 99,102
Increase (Decrease) in Stockholders' Equity [Roll Forward]
January 1, 2017 adoption of new accounting standard - See Note 2	0			83	(83)
Net income, excluding $2,774 attributable to redeemable noncontrolling interests	242,311				239,258		3,053
Other comprehensive income - change in fair value of interest rate swaps	1,835					1,835
Dividends declared to common shareholders	(213,954)				(213,954)
Dividends declared to preferred shareholders	(406)				(406)
Distributions declared to noncontrolling interests	(4,435)						(4,435)
Shares issued (in shares)		6,000	325,451
Shares issued	144,973	$ 150,000	$ 4					$ (5,027)	$ 42,694	$ 42,690
Exercise of stock options (in shares)			112,334
Exercise of stock options	8,214		$ 1	8,213
Shares issued under dividend reinvestment plan (in shares)			13,521
Shares issued under dividend reinvestment plan	1,809			1,809
Share-based compensation expense, net of forfeitures (in shares)			105,291
Share-based compensation expense, net of forfeitures	9,402		$ 1	9,401
Shares withheld for employee taxes (in shares)			(29,615)
Shares withheld for employee taxes	(4,216)			(4,216)
Conversion and redemption of OP units (in shares)			20,030
Conversion and redemption of OP units	0			(2,569)			(2,569)
Contributions from noncontrolling interests	35,264						35,264
Purchase of noncontrolling interest	(5,535)			43			(5,578)
Ending balance (in shares) at Sep. 30, 2017		405,896	72,542,909
Ending balance at Sep. 30, 2017	$ 2,333,791	$ 159,997	$ 728	$ 2,773,890	$ (724,919)	$ (742)	$ 124,837