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	4,090	$ 0	4,090	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		228
Issuance of common stock under Equity Incentive Plans, value	162	$ 1	161	0	0	0
Repurchase of common stock	(887)	0	0	0	0	(887)
Net loss	(56,863)	0	0	(56,863)	0	0
Unrealized gain on investments	3	$ 0	0	0	3	0
Balance, shares at Jun. 30, 2014		73,706
Balance, value at Jun. 30, 2014	116,668	$ 74	1,179,800	(1,060,821)	5	(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	3,741	$ 0	3,741	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		188
Issuance of common stock under Equity Incentive Plans, value	0	$ 0	0	0	0	0
Repurchase of common stock	(357)	0	0	0	0	(357)
Net loss	(56,150)	0	0	(56,150)	0	0
Unrealized gain on investments	161	0	0	0	161	0
Other	61	$ 0	61	0	0	0
Balance, shares at Jun. 30, 2015		103,851
Balance, value at Jun. 30, 2015	$ 231,474	$ 104	$ 1,394,421	$ (1,160,402)	$ 98	$ (2,747)