Employee Benefit Plans - Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Other long-term asset	$ 8,573	$ 6,721
Pension and other post-retirement liabilities	(229,868)	(341,510)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other long-term asset	8,573	6,721
Other current liability	(9,280)	(8,206)
Pension and other post-retirement liabilities	(228,579)	(339,872)
Amounts recognized in consolidated balance sheets	$ (229,286)	$ (341,357)