Consolidated Statements Of Equity - USD ($) $ in Thousands	Total	Common Shares Of Beneficial Interest	Additional Paid-In Capital	Distributions In Excess Of Net Income	Treasury Shares, At Cost	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Equity, Beginning Balance at Dec. 31, 2016	$ 3,095,553	$ 978	$ 3,678,277	$ (289,180)	$ (373,339)	$ (1,863)	$ 80,680
Net Income	200,860			196,422			4,438
Other comprehensive income	1,806					1,806
Proceeds from issuance of common shares	445,038	48	444,990
Net share awards	23,956		15,779		8,177
Employee share purchase plan	1,716		1,030		686
Common share options exercised	931		521		410
Change in classification of deferred compensation plan	(13,388)		(13,388)
Change in redemption value of non-qualified share awards	(10,038)			(10,038)
Diversification of share awards within deferred compensation plan	23,233		10,159	13,074
Conversions and redemptions of operating partnership units	0		117				(117)
Cash distributions declared to equity holders	(284,631)			(278,981)			(5,650)
Other	(322)	2	(324)
Equity, Ending Balance at Dec. 31, 2017	3,484,714	1,028	4,137,161	(368,703)	(364,066)	(57)	79,351
Net Income	160,694			156,128			4,566
Other comprehensive income	6,986					6,986
Proceeds from issuance of common shares	0
Net share awards	21,681		13,720		7,961
Employee share purchase plan	1,380		826		554
Common share options exercised	41		41
Change in classification of deferred compensation plan	(16,407)		(16,407)
Change in redemption value of non-qualified share awards	669			669
Diversification of share awards within deferred compensation plan	40,294		29,379	10,915
Treasury Stock, Value, Acquired, Par Value Method	(253)				(253)
Conversions and redemptions of operating partnership units	(14,415)		(9,781)				(4,634)
Cash distributions declared to equity holders	(300,107)			(294,505)			(5,602)
Other	(173)	3	(176)
Equity, Ending Balance at Dec. 31, 2018	3,385,104	1,031	4,154,763	(495,496)	(355,804)	6,929	73,681
Net Income	224,270			219,623			4,647
Other comprehensive income	(13,458)					(13,458)
Proceeds from issuance of common shares	353,213	36	353,177
Net share awards	20,199		13,609		6,590
Employee share purchase plan	2,333		1,538		795
Reclassifications of Temporary to Permanent Equity			43,311	9,363
Diversification of share awards within deferred compensation plan	52,674
Conversions and redemptions of operating partnership units	0		304				(304)
Cash distributions declared to equity holders	(323,264)			(317,657)			(5,607)
Other	653	2	29				622
Equity, Ending Balance at Dec. 31, 2019	$ 3,701,724	$ 1,069	$ 4,566,731	$ (584,167)	$ (348,419)	$ (6,529)	$ 73,039