Pension Plans - Accumulated Benefit Obligations in Excess of Plan Assets (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Defined Benefit Plan Plans With Benefit Obligations In Excess Of Plan Assets [Abstract] | ||
| Accumulated benefit obligation | $ 34,858 | $ 34,763 |
| Fair market value of assets | $ 24,435 | $ 23,136 |