CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Preferred Shares	Common Stock	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, 2016	$ 1,412,491	$ 94,016	$ 24	$ 2,800,736	$ (1,500,966)	$ (1,033)	$ 19,714
Beginning balance (in shares) at Dec. 31, 2016		1,935,400	238,037,177
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares	0			584			(584)
Redemption of noncontrolling OP units for common shares (in shares)			140,746
Exercise of employee common share options	478			478
Exercise of employee common share options, net (in shares)			151,106
Issuance of common shares and deferred compensation amortization, net	24,673			24,673
Issuance of common shares and deferred compensation amortization, net (in shares)			2,360,052
Acquisition of consolidated joint venture partner's equity interest	(7,951)			(7,951)
Dividends/distributions	(177,583)				(174,341)		(3,242)
Net Income	86,629				85,583		1,046
Other comprehensive income (loss)	2,098					2,098
Balance at end of period at Dec. 31, 2017	1,340,835	$ 94,016	$ 24	2,818,520	(1,589,724)	1,065	16,934
Ending 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
Repurchase of common shares	(49,858)			(49,858)
Repurchase of common shares (in shares)			(5,851,252)
Exercise of employee common share options	115			115
Exercise of employee common share options, net (in shares)			16,390
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 to settle tax obligations (in shares)			(271,792)
Repurchase of common shares to settle tax obligations	(2,544)			(2,544)
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 income (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
Repurchase of common shares	(958)			(958)
Repurchase of common shares (in shares)			(441,581)
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 to settle tax obligations (in shares)			(712,430)
Repurchase of common shares to settle tax obligations	(5,281)		$ (1)	(5,280)
Forfeiture of employee common shares	15				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
Other comprehensive income (loss)	(2,004)					(2,004)
Reallocation of noncontrolling interests				(973)			973
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