Employee Benefits - Summary of Accumulated Other Comprehensive Loss Expected to be Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Amortization of loss to be recognized in 2017	$ 297	$ 2,890	$ 8,544
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost to be recognized in 2017	(104)
Amortization of loss to be recognized in 2017	903
Supplemental Insurance/ Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost to be recognized in 2017	114
Amortization of loss to be recognized in 2017	$ 636