Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 62,754	$ 7,298
Restricted cash	550	550
Total cash, cash equivalents, and restricted cash	$ 63,304	$ 7,848	$ 30,354	$ 89,736