Pensions and Postretirement Benefits Other than Pensions - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost					$ 11,771	$ 13,559
Net periodic benefit cost					$ 64,842	$ 58,384
Pension Benefits - Domestic
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 2,465	$ 2,403	$ 4,930	$ 4,806
Interest cost	9,813	10,617	19,626	21,233
Expected return on plan assets	(13,514)	(13,391)	(27,029)	(26,783)
Amortization of actuarial loss	9,280	9,576	18,561	19,152
Net periodic benefit cost	8,044	9,205	16,088	18,408
Pension Benefits - International
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	2	0	4
Interest cost	2,860	3,737	5,630	7,461
Expected return on plan assets	(2,795)	(3,002)	(5,502)	(5,992)
Amortization of actuarial loss	1,351	1,361	2,661	2,717
Net periodic benefit cost	1,416	2,098	2,789	4,190
Other Postretirement Benefits
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	501	537	1,002	1,074
Interest cost	2,516	2,705	5,031	5,410
Amortization of prior service credit	(142)	(142)	(283)	(283)
Net periodic benefit cost	$ 2,875	$ 3,100	$ 5,750	$ 6,201