Retirement and Other Postretirement Benefit Plans - Schedule of Actual Allocations for the Pension Assets and Target Allocations by Asset Class (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Change in plan assets:
Percentage of Plan Assets	100.00%	100.00%
Target Allocations	100.00%	100.00%
Diversified Growth Funds
Change in plan assets:
Percentage of Plan Assets	24.10%	23.80%
Target Allocations	28.00%	28.10%
Liability Driven Investments
Change in plan assets:
Percentage of Plan Assets	17.20%	19.20%
Target Allocations	23.20%	23.20%
Index Linked Gilts
Change in plan assets:
Percentage of Plan Assets	30.90%	25.80%
Target Allocations	12.60%	12.60%
All Other Regions Equity Fund
Change in plan assets:
Percentage of Plan Assets	14.40%	16.60%
Target Allocations	19.70%	19.60%
U.K. Equity Fund
Change in plan assets:
Percentage of Plan Assets	9.70%	11.20%
Target Allocations	13.20%	13.30%
Diversified Investment, Funds
Change in plan assets:
Percentage of Plan Assets	1.10%	1.20%
Target Allocations	1.10%	1.20%
Insurance contracts
Change in plan assets:
Percentage of Plan Assets	2.30%	2.10%
Target Allocations	2.20%	2.00%
Cash and Cash Equivalents
Change in plan assets:
Percentage of Plan Assets	0.30%	0.10%