CONDENSED 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	Non-controlling Interests
Beginning Balance at Dec. 31, 2017	$ 1,340,835	$ 94,016	$ 24	$ 2,818,520	$ (1,589,724)	$ 1,065	$ 16,934
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares	0			63			(63)
Issuance of common shares and deferred compensation amortization, net	3,391			3,391
Repurchase of common shares	(7,362)			(7,362)
Repurchase of common shares to settle tax obligations	(2,544)			(2,544)
Forfeiture of employee common shares	(78)			(87)	9
Dividends/distributions	(89,361)				(87,441)		(1,920)
Net income (loss)	(15,618)				(16,009)		391
Other comprehensive income (loss)	33					33
Ending Balance at Jun. 30, 2018	1,229,296	94,016	24	2,811,981	(1,693,165)	1,098	15,342
Beginning Balance at Mar. 31, 2018	1,274,384	94,016	24	2,811,213	(1,647,804)	1,311	15,624
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares				63			(63)
Issuance of common shares and deferred compensation amortization, net	1,731			1,731
Repurchase of common shares	(1,026)			(1,026)
Dividends/distributions	(44,785)				(43,667)		(1,118)
Net income (loss)	(795)				(1,694)		899
Other comprehensive income (loss)	(213)					(213)
Ending Balance at Jun. 30, 2018	1,229,296	94,016	24	2,811,981	(1,693,165)	1,098	15,342
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	0			161			(161)
Issuance of common shares and deferred compensation amortization, net	3,096			3,096
Repurchase of common shares	(958)			(958)
Repurchase of common shares to settle tax obligations	(3,942)		(1)	(3,941)
Forfeiture of employee common shares	5				5
Dividends/distributions	(52,678)				(51,017)		(1,661)
Net income (loss)	52,049				51,360		689
Other comprehensive income (loss)	(76)					(76)
Ending Balance at Jun. 30, 2019	1,344,174	94,016	23	2,771,213	(1,536,752)	0	15,674
Beginning Balance at Mar. 31, 2019	1,345,334	94,016	23	2,769,822	(1,534,539)		16,012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of noncontrolling OP units for common shares				5			(5)
Issuance of common shares and deferred compensation amortization, net	1,386			1,386
Dividends/distributions	(26,315)				(25,546)		(769)
Net income (loss)	23,769				23,333		436
Other comprehensive income (loss)	0
Ending Balance at Jun. 30, 2019	$ 1,344,174	$ 94,016	$ 23	$ 2,771,213	$ (1,536,752)	$ 0	$ 15,674