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 |