Condensed Consolidated Statements of Changes in Stockholders' Equity - 3 months ended Mar. 31, 2018 - 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	(2,542,898)	(363)
Balances, in shares at Mar. 31, 2018		186,176
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized gain (loss) on equity securities for ASU 2016-01	$ 0			$ 2,604	$ (2,604)