Pension and Postretirement Benefits - Net Periodic Benefit Cost (Income) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension cost	$ 40	$ 40
Non-U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension cost	$ 600	$ 600