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 Income (Loss)	Noncontrolling Interests
Balance at beginning of period at Dec. 31, 2017	$ 1,340,835	$ 94,016	$ 24	$ 2,818,520	$ (1,589,724)	$ 1,065	$ 16,934
Beginning balance (in shares) at Dec. 31, 2017		1,935,400	240,689,081
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares	0			189			(189)
Redemption of noncontrolling OP units for common shares (in shares)			53,388
Issuance of common shares and deferred compensation amortization, net	6,520			6,520
Issuance of common shares and deferred compensation amortization, net (in shares)			966,791
Repurchase of common shares	(49,858)			(49,858)
Repurchase of common shares (in shares)			(5,851,252)
Repurchase of common shares to settle tax obligations	(2,544)			(2,544)
Repurchase of common shares to settle tax obligations (in shares)			(271,792)
Exercise of employee common share options	115			115
Exercise of employee common share options, net (in shares)			16,390
Forfeiture of employee common shares	(71)			(87)	16
Forfeiture of employee common shares (in shares)			(594,052)
Dividends/distributions	(178,236)				(174,807)		(3,429)
Net Income	230,906				227,415		3,491
Other comprehensive loss	(989)					(989)
Balance at end of period at Dec. 31, 2018	1,346,678	$ 94,016	$ 24	2,772,855	(1,537,100)	76	16,807
Ending balance (in shares) at Dec. 31, 2018		1,935,400	235,008,554
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of partnership interest in real estate	867						867
Redemption of noncontrolling OP units for common shares	0			1,655			(1,655)
Redemption of noncontrolling OP units for common shares (in shares)			391,993
Issuance of common shares and deferred compensation amortization, net	209,373		$ 2	209,371
Issuance of common shares and deferred compensation amortization, net (in shares)			20,579,745
Repurchase of common shares	(958)			(958)
Repurchase of common shares (in shares)			(441,581)
Repurchase of common shares to settle tax obligations	(5,281)		$ (1)	(5,280)
Repurchase of common shares to settle tax obligations (in shares)			(712,430)
Forfeiture of employee common shares	15			0	15
Forfeiture of employee common shares (in shares)			(55,562)
Dividends/distributions	(109,264)				(106,501)		(2,763)
Net Income	285,293				279,910		5,383
Reallocation of noncontrolling interests				(973)			973
Other comprehensive loss	(2,004)					(2,004)
Balance at end of period at Dec. 31, 2019	1,724,719	$ 94,016	$ 25	2,976,670	(1,363,676)	(1,928)	19,612
Ending balance (in shares) at Dec. 31, 2019		1,935,400	254,770,719
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	0			1,614			(1,614)
Redemption of noncontrolling OP units for common shares (in shares)			327,453
Issuance of common shares and deferred compensation amortization, net	231,699		$ 3	231,696
Issuance of common shares and deferred compensation amortization, net (in shares)			23,962,696
Repurchase of common shares	(11,042)			(11,042)
Repurchase of common shares (in shares)			(1,329,940)
Repurchase of common shares to settle tax obligations	(2,623)		$ 0	(2,623)
Repurchase of common shares to settle tax obligations (in shares)			(576,011)
Forfeiture of employee common shares	1				1
Forfeiture of employee common shares (in shares)			(2,467)
Dividends/distributions	(123,258)				(121,353)		(1,905)
Net Income	186,391				183,302		3,089
Other comprehensive loss	(16,035)					(16,035)
Balance at end of period at Dec. 31, 2020	$ 1,991,137	$ 94,016	$ 28	$ 3,196,315	$ (1,301,726)	$ (17,963)	$ 20,467
Ending balance (in shares) at Dec. 31, 2020		1,935,400	277,152,450