Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Tax Disclosure [Abstract]      
Federal statutory income tax rate (as a percent) 34.00% 34.00% 34.00%
Effective Income Tax Rate Reconciliation, Amount [Abstract]      
Effective tax rate (as a percent) 0.00% 0.00% 0.00%
Statutory rate of 34% $ (7,634) $ (4,416) $ (64)
State taxes, net of federal benefit (615) (256) (4)
Foreign rate differential 346 245 0
Stock-based compensation permanent differences 836 464 182
Meals and entertainment permanent differences 385 232 26
Miscellaneous permanent differences 165 32 13
Warrant fair market value adjustment (59) 229 0
Other adjustments (3) 474 0
Change in valuation allowance 6,579 2,996 (153)
Provision for income taxes $ 0 $ 0 $ 0