Pension and Other Post-Retirement Benefits - Weighted Average Asset Allocations of Domestic Funded Plans (Details) - UNITED STATES	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Target allocation, salaried employees	100.00%
Actual plan asset allocations, salaried employees	100.00%	100.00%
Target allocation, hourly employees	100.00%
Actual plan asset allocation, hourly employees	100.00%	100.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation, salaried employees	50.70%
Actual plan asset allocations, salaried employees	50.70%	53.10%
Target allocation, hourly employees	38.20%
Actual plan asset allocation, hourly employees	39.40%	48.60%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation, salaried employees	45.50%
Actual plan asset allocations, salaried employees	44.80%	41.20%
Target allocation, hourly employees	58.00%
Actual plan asset allocation, hourly employees	56.80%	45.40%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation, salaried employees	3.80%
Actual plan asset allocations, salaried employees	3.70%	4.60%
Target allocation, hourly employees	3.80%
Actual plan asset allocation, hourly employees	3.70%	5.90%
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation, salaried employees	0.00%
Actual plan asset allocations, salaried employees	0.80%	1.10%
Target allocation, hourly employees	0.00%
Actual plan asset allocation, hourly employees	0.10%	0.10%