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	$ 1.60
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	83,263			81,012			2,251
Other comprehensive income (loss)	(13,724)					(13,724)
Common shares issued	328,374	34	328,340
Net share awards	12,670		5,940		6,730
Employee share purchase plan	1,750		1,156		594
Change in classification of deferred compensation plan	52,674		43,311	9,363
Conversion of operating partnership units	0		115				(115)
Cash distributions declared to equity holders	(161,521)			(158,713)			(2,808)
Other	178		42				136
Ending balance at Jun. 30, 2019	$ 3,688,768	1,065	4,533,667	(563,834)	(348,480)	(6,795)	73,145
Cash distributions declared to equity holders per common share	$ 0.80
Beginning balance at Mar. 31, 2019	$ 3,726,320	1,064	4,527,659	(526,856)	(349,655)	616	73,492
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	43,542			42,399			1,143
Other comprehensive income (loss)	(7,411)					(7,411)
Net share awards	5,387		4,807		580
Employee share purchase plan	1,677		1,082		595
Conversion of operating partnership units	0		115				(115)
Cash distributions declared to equity holders	(80,780)			(79,377)			(1,403)
Other	33	1	4				28
Ending balance at Jun. 30, 2019	$ 3,688,768	1,065	4,533,667	(563,834)	(348,480)	(6,795)	73,145
Cash distributions declared to equity holders per common share	$ 1.66
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	61,978			59,761			2,217
Other comprehensive income (loss)	732					732
Common shares issued	0
Net share awards	13,525		7,146		6,379
Employee share purchase plan	1,043		640		403
Cash distributions declared to equity holders	(168,304)			(165,403)			(2,901)
Other	(131)	(1)	(130)
Ending balance at Jun. 30, 2020	$ 3,610,567	1,068	4,574,387	(689,809)	(341,637)	(5,797)	72,355
Cash distributions declared to equity holders per common share	$ 0.83
Beginning balance at Mar. 31, 2020	$ 3,671,324	1,069	4,569,995	(623,570)	(342,778)	(6,163)	72,771
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	17,511			16,477			1,034
Other comprehensive income (loss)	366					366
Net share awards	4,678		3,940		738
Employee share purchase plan	961		558		403
Cash distributions declared to equity holders	(84,166)			(82,716)			(1,450)
Other	(107)	(1)	(106)
Ending balance at Jun. 30, 2020	$ 3,610,567	$ 1,068	$ 4,574,387	$ (689,809)	$ (341,637)	$ (5,797)	$ 72,355