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, 2018	Dec. 31, 2017
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 1,698	$ 1,759
Sale proceeds (benefit payments)	(129)	(134)
Change in unrealized gain	(247)	(84)
Foreign exchange impact	(79)	157
Ending balance	$ 1,243	$ 1,698