Consolidated Statements Of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	AOCI	Accumulated Deficit
Balance, shares at Dec. 31, 2016		46,372
Balance, values at Dec. 31, 2016	$ 862,234	$ 463	$ 1,026,887	$ 4,906	$ (170,022)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases, shares		(708)
Share repurchases, value	(15,962)	$ (6)	(15,956)
Distribution reinvestment plan (DRIP), shares		820
Distribution reinvestment plan (DRIP), value	18,482	$ 10	18,472
Change in unrealized gain on interest rate swaps	180			180
Common distributions declared, $0.81 per share	(37,578)				(37,578)
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		1
Share-based compensation	27	$ 0	27
Net loss	(1,339)				(1,339)
Balance, shares at Jun. 30, 2017		46,485
Balance, values at Jun. 30, 2017	826,044	$ 467	1,029,430	5,086	(208,939)
Balance, shares at Dec. 31, 2017		46,584
Balance, values at Dec. 31, 2017	783,279	$ 468	1,031,685	6,459	(255,333)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2017-05 (see Note 2)	835				835
Balance, shares at Jan. 01, 2018		46,584
Balance, values at Jan. 01, 2018	784,114	$ 468	1,031,685	6,459	(254,498)
Balance, shares at Dec. 31, 2017		46,584
Balance, values at Dec. 31, 2017	$ 783,279	$ 468	1,031,685	6,459	(255,333)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases, shares	(600)	(601)
Share repurchases, value	$ (13,669)	$ (6)	(13,663)
Distribution reinvestment plan (DRIP), shares		761
Distribution reinvestment plan (DRIP), value	17,321	$ 8	17,313
Change in unrealized gain on interest rate swaps	7,878			7,878
Common distributions declared, $0.81 per share	(37,996)				(37,996)
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		1
Share-based compensation	27	$ 0	27
Net loss	(2,872)				(2,872)
Balance, shares at Jun. 30, 2018		46,745
Balance, values at Jun. 30, 2018	$ 754,803	$ 470	$ 1,035,362	$ 14,337	$ (295,366)