Consolidated Statement Of Shareholders' Equity - 6 months ended Jun. 30, 2018 - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Income	Noncontrolling Interests	Common Shares Additional Paid-in Capital
Beginning balance (in shares) at Dec. 31, 2017		405,896	73,090,877
Beginning balance at Dec. 31, 2017	$ 2,391,514	$ 159,997	$ 733	$ 2,855,321	$ (749,367)	$ 22	$ 124,808
Increase (Decrease) in Stockholders' Equity [Roll Forward]
January 1, 2018 adoption of new accounting standard - See Note 2	(6,028)				(6,028)
Net income, excluding $1,998 attributable to redeemable noncontrolling interests	126,466				124,842		1,624
Other comprehensive income - change in fair value of interest rate swaps	390					390
Dividends declared to common shareholders	(146,399)				(146,399)
Dividends declared to preferred shareholders	(4,021)				(4,021)
Distributions declared to noncontrolling interests	(2,767)						(2,767)
Shares issued (in shares)			148,614
Shares issued	18,320		$ 2					$ 18,318
Exercise of stock options (in shares)			93,593
Exercise of stock options	4,041		$ 1	4,040
Shares issued under dividend reinvestment plan (in shares)			9,292
Shares issued under dividend reinvestment plan	1,086			1,086
Share-based compensation expense, net of forfeitures (in shares)			99,574
Share-based compensation expense, net of forfeitures	7,144		$ 1	7,143
Shares withheld for employee taxes (in shares)			(7,007)
Shares withheld for employee taxes	(777)			(777)
Redemption of OP units	(4,386)			(360)			(4,026)
Contributions from noncontrolling interests	3,009						3,009
Ending balance (in shares) at Jun. 30, 2018		405,896	73,434,943
Ending balance at Jun. 30, 2018	$ 2,387,592	$ 159,997	$ 737	$ 2,884,771	$ (780,973)	$ 412	$ 122,648