Income Taxes - Summary of Reconciliation of Uncertain Tax Positions (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | |||
Beginning balance | $ 486 | $ 425 | $ 306 |
Addition for current year tax positions | 101 | 100 | 74 |
Addition for prior year tax positions | 16 | 2 | 45 |
Reduction for prior year positions | (52) | 0 | 0 |
Reduction for prior year positions resolved during the current year | (2) | (41) | 0 |
Ending balance | $ 549 | $ 486 | $ 425 |