Pension and Other Postretirement Benefits - Additional Information (Detail)		3 Months Ended
	Apr. 18, 2017 USD ($)	Mar. 31, 2017 USD ($) Installments
Defined Benefit Plan Disclosure [Line Items]
Cash contribution term to pension plan		30 months
Number of installments | Installments		3
Minimum required cash contribution to pension plan		$ 50,000,000
Aggregate cash cash contribution to pension plan		$ 150,000,000
Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
First payment to pension plan	$ 50,000,000