Retirement Plans (Actuarial Assumptions) (Details) - Pension Plan	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
UNITED STATES
Defined Benefit Plan Disclosure
Discount rate	3.90%	4.30%	4.30%
Expected rate of return on plan assets	5.90%	5.20%	5.20%
Foreign Plan
Defined Benefit Plan Disclosure
Discount rate	2.50%	2.70%	4.00%
Expected rate of return on plan assets	4.10%	4.40%	5.20%