Pensions - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Domestic Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	$ 314	$ 361	$ 434
Interest cost	1,297	1,383	1,411
Other	5	5	25
Net periodic benefit cost (income)	(299)	(277)	286
Foreign Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	423	372	380
Interest cost	693	678	678
Other	0	0	0
Net periodic benefit cost (income)	1,101	988	1,038
Pension Plan [Member] | Domestic Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	814	807	926
Interest cost	11,700	12,580	12,334
Expected return on plan assets	(16,012)	(15,835)	(17,685)
Amortization of prior service cost and actuarial loss	1,871	1,714	1,110
Settlements	0	0	0
Other	0	0	0
Net periodic benefit cost (income)	(1,627)	(734)	(3,315)
Pension Plan [Member] | Foreign Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	4,025	3,346	3,489
Interest cost	4,341	5,041	5,084
Expected return on plan assets	(2,617)	(3,133)	(3,373)
Amortization of prior service cost and actuarial loss	2,898	2,186	2,666
Settlements	6,427	538	132
Other	0	0	221
Net periodic benefit cost (income)	$ 15,074	$ 7,978	$ 8,219