Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2017	$ 814,977	$ 1,856	$ 3,357,345	$ (2,546,743)	$ 2,519
Balances, in shares at Dec. 31, 2017		185,638
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME (LOSS)	1,241			1,241
Other comprehensive income (loss)	(278)				(278)
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		538
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	(1,629)	$ 6	(1,635)
Balances at Mar. 31, 2018	814,311	$ 1,862	3,355,710	(2,541,898)	(363)
Balances, in shares at Mar. 31, 2018		186,176
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting standard	0			2,604	(2,604)
Balances at Dec. 31, 2018	852,512	$ 2,033	3,443,082	(2,592,544)	(59)
Balances, in shares at Dec. 31, 2018		203,310
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME (LOSS)	(19,201)			(19,201)
Other comprehensive income (loss)	59				59
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		1,801
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	(1,035)	$ 18	(1,053)
Balances at Mar. 31, 2019	$ 832,335	$ 2,051	$ 3,442,029	$ (2,611,745)	$ 0
Balances, in shares at Mar. 31, 2019		205,111