Pension Plans and Other Benefits - Plan Asset Allocations (Details) - Foreign Pension Plans Defined Benefit	12 Months Ended
	Dec. 31, 2017
Summary Target Allocation Strategy
Percentage over annualized rate of return of the consumer price index	5.00%
Fixed Income Securities
Summary Target Allocation Strategy
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	40.00%
Return Seeking Investments
Summary Target Allocation Strategy
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	60.00%