Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares [Member]	Capital in Excess of Par Value [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2013	$ (89,903)	$ 11	$ 1,643,660	$ (1,181)	$ (1,732,393)
Beginning Balance, Shares at Dec. 31, 2013		116,494
Sale of common stock, net of issuance costs	116,536	$ 1	116,535	0	0
Sale of common stock, Shares		9,775
Shares issued under equity compensation plans	46,984	$ 1	46,983	0	0
Shares issued under equity compensation plans, Shares		4,947
Stock-based compensation	17,017	$ 0	17,017	0	0
Other comprehensive loss	(386)	0	0	(386)	0
Net loss	(53,916)	0	0	0	(53,916)
Ending Balance at Dec. 31, 2014	36,332	$ 13	1,824,195	(1,567)	(1,786,309)
Ending Balance, Shares at Dec. 31, 2014		131,216
Shares issued under equity compensation plans	32,208	$ 0	32,208	0	0
Shares issued under equity compensation plans, Shares		4,073
Stock-based compensation	19,669	$ 0	19,669	0	0
Other comprehensive loss	(603)	0	0	(603)	0
Net loss	(81,177)	0	0	0	(81,177)
Ending Balance at Dec. 31, 2015	6,429	$ 13	1,876,072	(2,170)	(1,867,486)
Ending Balance, Shares at Dec. 31, 2015		135,289
Sale of common stock, net of issuance costs	189,276	$ 2	189,274	0	0
Sale of common stock, Shares		14,950
Shares issued under equity compensation plans	20,287	$ 0	20,287	0	0
Shares issued under equity compensation plans, Shares		2,973
Stock-based compensation	25,850	$ 0	25,850	0	0
Other comprehensive loss	(193)	0	0	(193)	0
Net loss	(153,524)	0	0	0	(153,524)
Ending Balance at Dec. 31, 2016	$ 88,125	$ 15	$ 2,111,483	$ (2,363)	$ (2,021,010)
Ending Balance, Shares at Dec. 31, 2016		153,212