Fair Value - Summary of Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Assets measured at fair value
Cash and cash equivalents	$ 87,634	$ 91,217
Restricted cash	6,779	6,389
Total Assets measured at fair value	94,413	97,606
Liabilities measured at fair value
Contingent consideration	13,045	12,418
Warrant liabilities	11,745	14,090
Total liabilities measured at fair value	24,790	26,508
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets measured at fair value
Cash and cash equivalents	87,634	91,217
Restricted cash	6,779	6,389
Total Assets measured at fair value	94,413	97,606
Significant Unobservable Inputs (Level 3) [Member]
Liabilities measured at fair value
Contingent consideration	13,045	12,418
Warrant liabilities	11,745	14,090
Total liabilities measured at fair value	$ 24,790	$ 26,508