Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Revenues	$ 8,528	$ 10,484	$ 16,977	$ 22,086
Cost of revenues	2,451	2,401	4,871	4,845
Gross profit	6,077	8,083	12,106	17,241
Operating expenses:
Selling and marketing	2,296	4,569	5,332	8,950
Research and development	3,609	5,900	7,858	11,836
General and administrative	3,418	4,862	7,296	9,804
Restructuring expense	2,435		2,435
Total operating expenses	11,758	15,331	22,921	30,590
Operating loss	(5,681)	(7,248)	(10,815)	(13,349)
Interest and other income (expense), net	(2)	8	(2)	20
Loss before provision for income taxes	(5,683)	(7,240)	(10,817)	(13,329)
Provision for income tax expense	12	4	45	73
Net loss	(5,695)	(7,244)	(10,862)	(13,402)
Other comprehensive income (loss), before tax:
Unrealized holding gains (losses) on available-for-sale securities	1	(17)	1	1
Income tax expense related to items of other comprehensive income (expense)	0	0	0	0
Other comprehensive income (expense), net of tax	1	(17)	1	1
Comprehensive loss	$ (5,694)	$ (7,261)	$ (10,861)	$ (13,401)
Net loss per share:
Basic and diluted	$ (0.15)	$ (0.19)	$ (0.28)	$ (0.36)
Weighted average shares outstanding:
Basic and diluted	38,518	37,247	38,118	36,932