Pension and Other Postretirement Benefit Plans Actuarial Assumptions Used to Determine the Actuarial Present Value of Projected Benefit Obligation and Net Periodic Pensions Costs (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension and Other Postretirement Benefit Plans [Abstract]
Defined Benefit Plan, Weighted Average Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost, Discount Rate	2.00%	1.90%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Benefit Cost, Expected Long-Term Return on Plan Assets	2.00%	1.90%
Defined Benefit Plan, Weighted Average Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost, Rate of Compensation Increase	2.90%	2.75%