Pension Plans Weighted Average Assumptions Used to Determine Net Periodic Pension Cost (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
United States Pension Plan of US Entity [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.83%
Expected long-term return on plan assets	5.75%
Foreign Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.91%	2.63%
Expected long-term return on plan assets	3.58%	4.19%
Rate of compensation increase	2.89%	2.77%