Consolidated Statement Of Shareholders' Equity - 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, 2013		399,896	66,701,422
Beginning balance at Dec. 31, 2013	$ 1,471,297	$ 9,997	$ 667	$ 2,062,708	$ (623,795)	$ (1,417)	$ 23,137
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amount attributable to redeemable noncontrolling interests	168,837				164,535		4,302
Other comprehensive income (loss) - change in value of interest rate swaps	(2,098)					(2,098)
Dividends declared to common shareholders	(224,190)				(224,190)
Dividends declared to preferred shareholders	(541)				(541)
Distributions declared to noncontrolling interests	(4,620)						(4,620)
Common shares issued (in shares)			1,768,703
Common shares issued	213,580		$ 18	213,562
Exercise of stock options (in shares)			29,218
Exercise of stock options	$ 2,262		$ 1	2,261
Shares issued under dividend reinvestment plan (in shares)	18,705		18,705
Shares issued under dividend reinvestment plan	$ 2,168			2,168
Share-based compensation expense, net of forfeitures (in shares)			117,647
Share-based compensation expense, net of forfeitures	12,941		$ 1	12,940
Shares withheld for employee taxes (in shares)			(29,912)
Adjustments Related to Tax Withholding for Share-based Compensation				3,335
Shares withheld for employee taxes	(3,335)
Conversion and redemption of OP units	63			49			14
Contributions from noncontrolling interests	65,350						65,350
Adjustment to redeemable noncontrolling interests	(9,032)			(9,032)
Ending balance (in shares) at Dec. 31, 2014		399,896	68,605,783
Ending 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 amount attributable to redeemable noncontrolling interests	215,001				210,219		4,782
Other comprehensive income (loss) - change in value of interest rate swaps	(595)					(595)
Dividends declared to common shareholders	(250,388)				(250,388)
Dividends declared to preferred shareholders	(541)				(541)
Distributions declared to noncontrolling interests	(5,269)						(5,269)
Common shares issued (in shares)			813,548
Common shares issued	108,545		$ 8	108,537
Exercise of stock options (in shares)			29,940
Exercise of stock options	$ 1,991			1,991
Shares issued under dividend reinvestment plan (in shares)	16,524		16,524
Shares issued under dividend reinvestment plan	$ 2,296			2,296
Share-based compensation expense, net of forfeitures (in shares)			52,213
Share-based compensation expense, net of forfeitures	12,074		$ 1	12,073
Shares withheld for employee taxes (in shares)			(64,227)
Adjustments Related to Tax Withholding for Share-based Compensation				9,211
Shares withheld for employee taxes	(9,211)
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	34,737						34,737
Adjustment to redeemable noncontrolling interests	(19,114)			(19,114)
Ending balance (in shares) at Dec. 31, 2015		399,896	69,493,392
Ending 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 amount attributable to redeemable noncontrolling interests	256,170				249,910		6,260
Other comprehensive income (loss) - change in value of interest rate swaps	1,533					1,533
Dividends declared to common shareholders	(274,402)				(274,402)
Dividends declared to preferred shareholders	(541)				(541)
Distributions declared to noncontrolling interests	(7,546)						(7,546)
Common shares issued (in shares)			2,156,671
Common shares issued	$ 324,191		$ 21	324,170
Exercise of stock options (in shares)	55,365		55,365
Exercise of stock options	$ 4,542		$ 1	4,541
Shares issued under dividend reinvestment plan (in shares)	15,619		15,619
Shares issued under dividend reinvestment plan	$ 2,387			2,387
Share-based compensation expense, net of forfeitures (in shares)			134,913
Share-based compensation expense, net of forfeitures	11,227		$ 2	11,225
Shares withheld for employee taxes (in shares)			(30,671)
Adjustments Related to Tax Withholding for Share-based Compensation				4,451
Shares withheld for employee taxes	(4,451)
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	885						885
Adjustment to redeemable noncontrolling interests	(20,091)			(20,091)
Ending balance (in shares) at Dec. 31, 2016		399,896	71,995,897
Ending balance at Dec. 31, 2016	$ 2,075,835	$ 9,997	$ 722	$ 2,718,325	$ (749,734)	$ (2,577)	$ 99,102