Postretirement Benefit Plans - Weighted Average Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
U.S. | Defined benefit plan
Weighted average assumptions used to determine benefit obligations:
Discount rate (in percent)	3.75%	4.29%
Long-term pay progression (in percent)	3.30%	3.30%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate (in percent)	4.21%	4.40%
Long term rate of return on plan assets (in percent)	4.30%	4.60%
Long-term pay progression (in percent)	3.30%	3.30%
U.S. | Retiree health care plan
Weighted average assumptions used to determine benefit obligations:
Discount rate (in percent)	3.63%	4.08%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate (in percent)	4.08%	4.40%
Long term rate of return on plan assets (in percent)	4.10%	4.40%
Non-U.S. | Defined benefit plan
Weighted average assumptions used to determine benefit obligations:
Discount rate (in percent)	1.84%	1.76%
Long-term pay progression (in percent)	2.96%	3.11%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate (in percent)	1.76%	2.41%
Long term rate of return on plan assets (in percent)	2.60%	3.18%
Long-term pay progression (in percent)	3.11%	3.21%