Significant Accounting Policies - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 14,680	$ 25,342
Restricted cash	10	10
Total assets	14,690	25,352
Warrant liability		5
Contingent consideration	39,600	45,100
Total liabilities	39,600	45,105
Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	14,680	25,342
Restricted cash	10	10
Total assets	14,690	25,352
Warrant liability		0
Contingent consideration	0	0
Total liabilities	0	0
Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Restricted cash	0	0
Total assets	0	0
Warrant liability		0
Contingent consideration	0	0
Total liabilities	0	0
Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Restricted cash	0	0
Total assets	0	0
Warrant liability		5
Contingent consideration	39,600	45,100
Total liabilities	$ 39,600	$ 45,105