Supplemental Disclosures to the Unaudited Condensed Consolidated Balance Sheets and Unaudited Condensed Consolidated Statements of Cash Flows - Summary of Cash and Cash Equivalents Reconciliation (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 7,408	$ 49,704
Restricted cash	325	325
Total cash, cash equivalents and restricted cash	$ 7,733	$ 50,029	$ 12,187	$ 6,392