Employee Benefit Plans - Components of Net Periodic Defined Benefit Cost (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Defined Benefit Pension Plans | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Interest cost | $ 2,302 | $ 2,376 | $ 2,538 |
| Expected return on plan assets | (2,911) | (3,353) | (3,409) |
| Amortization of actuarial (gain) loss | 1,474 | 1,340 | 934 |
| Total | 865 | 363 | 63 |
| OPEB | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Interest cost | 96 | 108 | 114 |
| Amortization of actuarial (gain) loss | (152) | (101) | (176) |
| Amortization of prior service credit | (541) | (621) | (644) |
| Total | $ (597) | $ (614) | $ (706) |