Health Care, Pension and Other Benefits - Components of Net Periodic Benefit Costs (Credits) for Domestic Defined Benefit Pension Plans, Foreign Defined Benefit Pension Plans and Postretirement Benefits Other Than Pensions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Postretirement Benefits Other than Pensions
Net periodic benefit (credit) cost:
Service cost	$ 499	$ 524	$ 1,496	$ 1,538
Interest cost	2,545	2,755	7,634	7,991
Expected return on assets
Recognition of:
Unrecognized prior service cost	(1,643)	(1,645)	(4,927)	(4,935)
Unrecognized actuarial loss	581	8	1,744	24
Ongoing pension (credit) cost			5,947	4,618
Settlements				(9,332)
Net periodic benefit (credit) cost	1,982	1,642	5,947	(4,714)
Domestic Defined Benefit Pension Plans | Defined Benefit Pension Plans
Net periodic benefit (credit) cost:
Service cost	1,158	5,356	6,673	16,128
Interest cost	8,541	8,734	25,233	22,335
Expected return on assets	(14,383)	(13,351)	(43,199)	(34,959)
Recognition of:
Unrecognized prior service cost	407	341	1,192	1,022
Unrecognized actuarial loss		1,334		4,657
Ongoing pension (credit) cost			(10,101)	9,183
Settlements			825
Net periodic benefit (credit) cost	(4,277)	2,414	(9,276)	9,183
Foreign Defined Benefit Pension Plans | Defined Benefit Pension Plans
Net periodic benefit (credit) cost:
Service cost	2,016	2,050	6,048	6,255
Interest cost	2,352	2,242	7,055	5,744
Expected return on assets	(2,685)	(2,488)	(8,055)	(6,260)
Recognition of:
Unrecognized prior service cost
Unrecognized actuarial loss	383	474	1,149	324
Ongoing pension (credit) cost			6,197	6,063
Settlements
Net periodic benefit (credit) cost	$ 2,066	$ 2,278	$ 6,197	$ 6,063