Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
Dec. 31, 2017 |
|
| Income Tax Disclosure [Abstract] | |||||
| Income tax expenses (benefits) | $ 1,521 | $ 538 | $ 2,511 | $ 1,391 | |
| Net operating loss carryforward, utilization limitation | 70.00% | 70.00% | |||
| Statutory income tax rate | 21.00% | 35.00% | |||