Retirement Plans and Other Postretirement Benefits - Expected Amortization Expense (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	$ 1,389
Accretion of prior service cost	(282)
Other Post Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	204
Accretion of prior service cost	$ 0