Employee Benefit Plans - Changes in Other Comprehensive Income (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Defined Benefit Pension Plans | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Net actuarial gain (loss) arising during the year | $ (2,373) | $ (9,519) | $ 5,305 |
| Amortization of actuarial (gain) loss | 1,340 | 934 | 1,238 |
| Total | (1,033) | (8,585) | 6,543 |
| OPEB | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Net actuarial gain (loss) arising during the year | 336 | (385) | 240 |
| Amortization of actuarial (gain) loss | (101) | (176) | (146) |
| Amortization of prior service credit | (621) | (644) | (688) |
| Total | $ (386) | $ (1,205) | $ (594) |