Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss federal state	$ 30,836	$ 22,442
Research credits	12,307	10,694
Accrued compensation and vacation	411	390
Deferred revenue, other accruals and reserves	3,918	3,077
Stock compensation	4,319	4,028
Patents	2,884	4,472
Gross deferred tax assets	54,675	45,103
Valuation allowance	(54,420)	(45,036)
Total deferred tax asset	255	67
Deferred tax liabilities:
Property and equipment	255	67
Total deferred tax liabilities	255	67
Valuation Allowance
Increase in valuation allowance	$ 9,400	$ 9,500