Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenues	$ 36,979	$ 42,675	$ 43,329
Cost of revenues	9,317	9,707	8,448
Gross profit	27,662	32,968	34,881
Operating expenses:
Selling and marketing	9,559	15,675	16,666
Research and development	14,192	21,305	24,767
General and administrative	13,218	18,216	20,211
Restructuring expenses	2,435	5,602	238
Total operating expenses	39,404	60,798	61,882
Operating loss	(11,742)	(27,830)	(27,001)
Non-operating income:
Change in fair value of contingent liability			1,210
Interest and other income (expense), net	(8)	30	94
Loss before provision for income taxes	(11,750)	(27,800)	(25,697)
Provision for income tax expense (benefit)	49	153	(234)
Net loss	(11,799)	(27,953)	(25,463)
Other comprehensive income (loss), before tax:
Unrealized holding gains on available-for-sale securities		7	33
Income tax expense related to items of other comprehensive income			6
Other comprehensive income, net of tax		7	27
Comprehensive loss	$ (11,799)	$ (27,946)	$ (25,436)
Net loss per share:
Basic and diluted	$ (0.29)	$ (0.76)	$ (0.71)
Weighted average shares outstanding:
Basic and diluted	40,649	36,982	35,849