Employee Benefit Plans (Other Pension Assumptions) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase (average)	3.50%	3.50%
Assumed health care cost trend rate Initial trend	6.75%	7.00%
Assumed health care cost trend rate Ultimate trend	5.00%	5.00%
Assumed health care cost trend rate Year ultimate reached	2025	2025
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.60%	4.00%
Nonqualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.45%	3.80%
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.55%	3.90%