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 Income/(Loss)	Noncontrolling Interests	Common shares	Preferred Shares	Preferred Shares Additional Paid-in Capital
Contributions from noncontrolling interests	$ 885						$ 885
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 amount attributable to redeemable noncontrolling interests	256,170				249,910		6,260
Other comprehensive (loss) income - 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)
Shares issued (in shares)			2,156,671
Shares issued	324,191		$ 21	324,170
Exercise of stock options (in shares)			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)
Shares withheld for employee taxes	(4,451)			(4,451)
Conversion and redemption of OP units (in shares)			170,608
Conversion and redemption of OP units	0		$ 2	18,677			(18,679)
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
Contributions from noncontrolling interests	35,331						35,331
Increase (Decrease) in Stockholders' Equity [Roll Forward]
January 1 adoption of new accounting standard - See Note 2	0			83	(83)
Net income, excluding amount attributable to redeemable noncontrolling interests	293,996				289,914		4,082
Other comprehensive (loss) income - change in value of interest rate swaps	2,599					2,599
Dividends declared to common shareholders	(287,006)				(287,006)
Dividends declared to preferred shareholders	(2,458)				(2,458)
Distributions declared to noncontrolling interests	(5,560)						(5,560)
Shares issued (in shares)		6,000	826,592
Shares issued	108,248	$ 150,000	$ 8	108,240					$ 144,965	$ (5,035)
Exercise of stock options (in shares)			152,634
Exercise of stock options	$ 9,979		$ 2	9,977
Shares issued under dividend reinvestment plan (in shares)	17,911		17,911
Shares issued under dividend reinvestment plan	$ 2,373			2,373
Share-based compensation expense, net of forfeitures (in shares)			107,522
Share-based compensation expense, net of forfeitures	12,371		$ 1	12,370
Shares withheld for employee taxes (in shares)			(29,709)
Shares withheld for employee taxes	(4,229)			(4,229)
Conversion and redemption of OP units (in shares)			20,030
Conversion and redemption of OP units	0		$ 0	2,569			(2,569)
Purchase of noncontrolling interests	(5,536)			42			(5,578)
Adjustment to redeemable noncontrolling interests	10,606			10,606
Ending balance (in shares) at Dec. 31, 2017		405,896	73,090,877
Ending balance at Dec. 31, 2017	2,391,514	$ 159,997	$ 733	2,855,321	(749,367)	22	124,808
Contributions from noncontrolling interests	4,020						4,020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
January 1 adoption of new accounting standard - See Note 2	(6,028)				(6,028)
Net income, excluding amount attributable to redeemable noncontrolling interests	245,161				241,907		3,254
Other comprehensive (loss) income - change in value of interest rate swaps	(438)					(438)
Dividends declared to common shareholders	(297,347)				(297,347)
Dividends declared to preferred shareholders	(8,042)				(8,042)
Distributions declared to noncontrolling interests	$ (5,175)						(5,175)
Shares issued (in shares)			987,461
Shares issued			$ 10	126,061				$ 126,071
Exercise of stock options (in shares)	105,803		105,803
Exercise of stock options	$ 4,572		$ 1	4,571
Shares issued under dividend reinvestment plan (in shares)	17,952		17,952
Shares issued under dividend reinvestment plan	$ 2,159			2,159
Share-based compensation expense, net of forfeitures (in shares)			55,223
Share-based compensation expense, net of forfeitures	12,736		$ 1	12,735
Shares withheld for employee taxes (in shares)			(8,432)
Shares withheld for employee taxes	(958)			(958)
Conversion and redemption of OP units (in shares)			749
Conversion and redemption of OP units	(6,012)		$ 0	(544)			(5,468)
Adjustment to redeemable noncontrolling interests	5,097			5,097
Ending balance (in shares) at Dec. 31, 2018		405,896	74,249,633
Ending balance at Dec. 31, 2018	$ 2,467,330	$ 159,997	$ 745	$ 3,004,442	$ (818,877)	$ (416)	$ 121,439