Postretirement Benefit Plans - Fair Value Changes Within Asset Categories for which Fair Value Measurements Use Significant Unobservable Inputs Level 3 (Detail) - Insurance Contracts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 1,969	$ 2,241
Sale proceeds (benefit payments)	(144)	(168)
Change in unrealized gain	265	11
Foreign exchange impact	(331)	(115)
Ending balance	$ 1,759	$ 1,969