Employee Pension Plans - Additional Information (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract] | |||
| Contribution to defined contribution plans | $ 4.3 | $ 4.1 | $ 4.0 |