Condensed Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (4,562)	$ (9,262)	$ (19,416)	$ (31,489)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities, net of tax expense of $160 for the three months and tax benefit of $89 for the nine months ended September 30, 2014, and $17 for the three months and $172 for the nine months ended September 30, 2013.	(261)	32	145	275
Other comprehensive income (loss)	(261)	32	145	275
Total comprehensive loss	$ (4,823)	$ (9,230)	$ (19,271)	$ (31,214)