CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-in-Capital	Accumulated Distributions in Excess of Net Income	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Beginning Balance at Dec. 31, 2018	$ 1,346,678	$ 94,016	$ 24	$ 2,772,855	$ (1,537,100)	$ 76	$ 16,807
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares				504			(504)
Issuance of common shares and deferred compensation amortization, net	136,585		2	136,583
Repurchase of common shares	(958)			(958)
Repurchase of common shares to settle tax obligations	(5,281)		(1)	(5,280)
Forfeiture of employee common shares	15				15
Dividends/distributions	(80,249)				(78,053)		(2,196)
Net income	199,870				194,679		5,191
Other comprehensive loss	(5,625)					(5,625)
Ending Balance at Sep. 30, 2019	1,591,035	94,016	25	2,903,704	(1,420,459)	(5,549)	19,298
Beginning Balance at Jun. 30, 2019	1,344,174	94,016	23	2,771,213	(1,536,752)		15,674
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares	0			343			(343)
Issuance of common shares and deferred compensation amortization, net	133,489		2	133,487
Repurchase of common shares to settle tax obligations	(1,339)			(1,339)
Forfeiture of employee common shares	10				10
Dividends/distributions	(27,571)				(27,036)		(535)
Net income	147,821				143,319		4,502
Other comprehensive loss	(5,549)					(5,549)
Ending Balance at Sep. 30, 2019	1,591,035	94,016	25	2,903,704	(1,420,459)	(5,549)	19,298
Beginning Balance at Dec. 31, 2019	1,724,719	94,016	25	2,976,670	(1,363,676)	(1,928)	19,612
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of partnership interest in real estate	1,285						1,285
Redemption of noncontrolling OP units for common shares				632			(632)
Issuance of common shares and deferred compensation amortization, net	230,117		3	230,114
Repurchase of common shares	(11,042)			(11,042)
Repurchase of common shares to settle tax obligations	(2,623)			(2,623)
Forfeiture of employee common shares	1			0	1
Dividends/distributions	(91,518)				(89,997)		(1,521)
Net income	81,169				78,924		2,245
Other comprehensive loss	(17,759)					(17,759)
Ending Balance at Sep. 30, 2020	1,914,349	94,016	28	3,193,751	(1,374,748)	(19,687)	20,989
Beginning Balance at Jun. 30, 2020	1,892,186	94,016	28	3,185,458	(1,386,001)	(20,730)	19,415
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of partnership interest in real estate	398						398
Redemption of noncontrolling OP units for common shares				150			(150)
Issuance of common shares and deferred compensation amortization, net	8,143		0	8,143
Dividends/distributions	(31,039)				(30,651)		(388)
Net income	43,618				41,904		1,714
Other comprehensive loss	1,043					1,043
Ending Balance at Sep. 30, 2020	$ 1,914,349	$ 94,016	$ 28	$ 3,193,751	$ (1,374,748)	$ (19,687)	$ 20,989