Postretirement Benefits Other Than Pensions - Schedule of Net Periodic Benefit Costs for Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 314	$ 361	$ 434
Interest cost	1,297	1,383	1,411
Amortization of prior service credit and recognized actuarial gain	(1,915)	(2,026)	(1,584)
Other	5	5	25
Net periodic benefit cost (income)	(299)	(277)	286
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	423	372	380
Interest cost	693	678	678
Amortization of prior service credit and recognized actuarial gain	(15)	(62)	(20)
Other	0	0	0
Net periodic benefit cost (income)	$ 1,101	$ 988	$ 1,038