Condensed 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 (loss)/income	Non-controlling interests
Cash distributions declared to equity holders per common share	$ 0.80
Beginning balance at Dec. 31, 2018	$ 3,385,104	$ 1,031	$ 4,154,763	$ (495,496)	$ (355,804)	$ 6,929	$ 73,681
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	39,721			38,613			1,108
Other comprehensive income (loss)	(6,313)					(6,313)
Common shares issued	328,374	34	328,340
Net share awards	7,283		1,133		6,150
Employee share purchase plan	73		74		(1)
Change in classification of deferred compensation plan	52,674		43,311	9,363
Cash distributions declared to equity holders	(80,741)			(79,336)			(1,405)
Other	145	(1)	38				108
Ending balance at Mar. 31, 2019	$ 3,726,320	1,064	4,527,659	(526,856)	(349,655)	616	73,492
Cash distributions declared to equity holders per common share	$ 0.83
Beginning balance at Dec. 31, 2019	$ 3,701,724	1,069	4,566,731	(584,167)	(348,419)	(6,529)	73,039
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	44,467			43,284			1,183
Other comprehensive income (loss)	366					366
Common shares issued	0
Net share awards	8,847		3,206		5,641
Employee share purchase plan	82		82
Cash distributions declared to equity holders	(84,138)			(82,687)			(1,451)
Other	(24)		(24)
Ending balance at Mar. 31, 2020	$ 3,671,324	$ 1,069	$ 4,569,995	$ (623,570)	$ (342,778)	$ (6,163)	$ 72,771