Significant Accounting Policies - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 50,422	$ 14,680
Restricted cash	20	10
Total assets	50,442	14,690
Contingent consideration	48,400	39,600
Total liabilities	48,400	39,600
Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	50,422	14,680
Restricted cash	20	10
Total assets	50,442	14,690
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
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
Contingent consideration	48,400	39,600
Total liabilities	$ 48,400	$ 39,600