Fair Value Measurements - Fair Value of Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities related to Warrants	$ 216	$ 322
Derivative instrument liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities related to Warrants	216	322	$ 172
Fair value on a recurring basis | Warrants | Derivative instrument liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities related to Warrants	216	322
Fair value on a recurring basis | Warrants | Derivative instrument liability | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities related to Warrants	$ (106)	$ 322