Income Taxes - Schedule of Company's Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating losses	$ 20,139	$ 28,677
Credits	1,654	1,414
Accruals and reserves	643	519
Deferred revenue and contract costs	464	871
Gross deferred tax assets	22,900	31,481
Valuation allowance	(22,789)	(31,143)
Net deferred tax assets	111	338
Deferred tax liabilities:
Fixed assets and intangibles	$ (111)	$ (338)