Income Taxes - Changes in Unrecognized Tax Benefits Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Income Tax Disclosure [Abstract] | |||
| Balance at January 1 | $ 178 | $ 794 | $ 608 |
| Additions for tax positions of prior years | 0 | 0 | 186 |
| Reductions for tax positions of prior years | 0 | (616) | 0 |
| Expiration of statutes of limitations | (178) | 0 | 0 |
| Balance at December 31 | $ 0 | $ 178 | $ 794 |