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, 2013	$ 2,760,181	$ 967	$ 3,596,069	$ (494,167)	$ (410,227)	$ (1,106)	$ 68,645
Net Income	301,314			292,089			9,225
Other comprehensive loss	(1,313)					(1,313)
Common shares issued	66,225	9	66,216
Net share awards	19,368		8,010		11,358
Employee share purchase plan	2,271		1,012		1,259
Common share options exercised	1,502	1	517		984
Change in classification of deferred compensation plan	(7,702)		(7,702)
Change in redemption value of non-qualified share awards	(17,921)			(17,921)
Diversification of share awards within deferred compensation plan	4,669		3,273	1,396
Conversions and redemptions of operating partnership units	0		52				(52)
Cash distributions declared to equity holders	(240,185)			(235,174)			(5,011)
Other		(1)	1
Equity, Ending Balance at Dec. 31, 2014	2,888,409	976	3,667,448	(453,777)	(396,626)	(2,419)	72,807
Net Income	258,262			249,315			8,947
Other comprehensive loss	506					506
Net share awards	22,325		13,020		9,305
Employee share purchase plan	1,111		583		528
Common share options exercised	176		176
Change in classification of deferred compensation plan	(10,999)		(10,999)
Change in redemption value of non-qualified share awards	(3,788)			(3,788)
Diversification of share awards within deferred compensation plan	3,557		2,134	1,423
Conversions and redemptions of operating partnership units	0		86				(86)
Cash distributions declared to equity holders	(257,059)			(251,750)			(5,309)
Purchase of non-controlling interests	(9,500)		(9,480)				(20)
Other	(104)		(104)
Equity, Ending Balance at Dec. 31, 2015	2,892,896	976	3,662,864	(458,577)	(386,793)	(1,913)	76,339
Net Income	838,226			819,823			18,403
Other comprehensive loss	50					50
Net share awards	24,996		15,213		9,783
Employee share purchase plan	1,697		944		753
Common share options exercised	3,921		1,003		2,918
Change in classification of deferred compensation plan	(13,956)		(13,956)
Change in redemption value of non-qualified share awards	(9,145)			(9,145)
Diversification of share awards within deferred compensation plan	25,428		11,931	13,497
Conversions and redemptions of operating partnership units	(80)		290				(370)
Cash distributions declared to equity holders	(668,470)			(654,778)			(13,692)
Other	(10)	2	(12)
Equity, Ending Balance at Dec. 31, 2016	$ 3,095,553	$ 978	$ 3,678,277	$ (289,180)	$ (373,339)	$ (1,863)	$ 80,680