Cash and Restricted Cash - Summary of Reconciliation of Cash and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 7,778	$ 9,167	$ 4,819
Restricted cash	422	292	348
Total cash and restricted cash	$ 8,200	$ 9,459	$ 5,167	$ 23,923