CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Cumulative Distributions and Net Income (Loss)
Balance (in shares) at Dec. 31, 2016		188,719,952
Balance at Dec. 31, 2016	$ 716,907	$ 1,887	$ 1,679,524	$ (964,504)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	25,114			25,114
Redemptions of common stock (in shares)		(1,053,650)
Redemptions of common stock	(5,767)	$ (10)	(5,757)
Distributions declared	$ (51,672)			(51,672)
Balance (in shares) at Dec. 31, 2017	187,666,302	187,666,302
Balance at Dec. 31, 2017	$ 684,582	$ 1,877	1,673,767	(991,062)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(979)			(979)
Redemptions of common stock (in shares)		(261,092)
Redemptions of common stock	(1,277)	$ (3)	(1,274)
Transfers from redeemable common stock	1,277		1,277
Distributions declared	$ (11,309)			(11,309)
Balance (in shares) at Mar. 31, 2018	187,405,210	187,405,210
Balance at Mar. 31, 2018	$ 672,294	$ 1,874	$ 1,673,770	$ (1,003,350)