Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Gain (Loss)	Treasury Stock
Balance, shares at Dec. 31, 2013		73,478
Balance, value at Dec. 31, 2013	$ 170,163	$ 73	$ 1,175,549	$ (1,003,958)	$ 2	$ (1,503)
Stock-based compensation	5,584	$ 0	5,584	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		252
Issuance of common stock under Equity Incentive Plans, value	325	$ 1	324	0	0	0
Repurchase of common stock	(887)	0	0	0	0	(887)
Net loss	(97,361)	$ 0	0	(97,361)	0	0
Unrealized gain on investments	0
Balance, shares at Sep. 30, 2014		73,730
Balance, value at Sep. 30, 2014	77,824	$ 74	1,181,457	(1,101,319)	2	(2,390)
Balance, shares at Dec. 31, 2014		103,663
Balance, value at Dec. 31, 2014	284,018	$ 104	1,390,619	(1,104,252)	(63)	(2,390)
Stock-based compensation	5,413	$ 0	5,413	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		197
Issuance of common stock under Equity Incentive Plans, value	114	$ 0	114	0	0	0
Repurchase of common stock	(357)	0	0	0	0	(357)
Net loss	(91,432)	0	0	(91,432)	0	0
Unrealized gain on investments	121	0	0	0	121	0
Other	61	$ 0	61	0	0	0
Balance, shares at Sep. 30, 2015		103,860
Balance, value at Sep. 30, 2015	$ 197,938	$ 104	$ 1,396,207	$ (1,195,684)	$ 58	$ (2,747)