Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Deferred tax assets:    
Net operating loss federal state $ 15,411 $ 12,515
Research credits 8,727 5,810
Accrued compensation and vacation 595 1,201
Deferred revenue, other accruals and reserves 2,188 574
Stock compensation 3,262 1,822
Patents 5,929 8,118
Gross deferred tax assets 36,112 30,040
Valuation allowance (35,496) (29,199)
Total deferred tax asset 616 841
Deferred tax liabilities:    
Property and equipment 616 841
Total deferred tax liabilities 616 841
Net deferred tax assets $ 0 $ 0