Pensions and Postretirement Benefits Other than Pensions - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	$ 487	$ 501
Interest cost	2,313	2,515
Amortization of prior service credit	(135)	(141)
Net periodic benefit cost	2,665	2,875
Domestic | Pension Benefits
Components of net periodic benefit cost:
Service cost	2,580	2,465
Interest cost	9,210	9,813
Expected return on plan assets	(13,498)	(13,515)
Amortization of actuarial loss	8,235	9,281
Net periodic benefit cost	6,527	8,044
International | Pension Benefits
Components of net periodic benefit cost:
Service cost	0	0
Interest cost	2,906	2,770
Expected return on plan assets	(3,155)	(2,707)
Amortization of actuarial loss	1,110	1,310
Net periodic benefit cost	$ 861	$ 1,373