Employee and Retiree Benefit Plans (Weighted Average Asset Allocation for Funded Pension Benefit Plans) (Details)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	100.00%	100.00%
Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	60.30%	58.40%
Defined Benefit Plan, Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	37.20%	39.00%
Defined Benefit Plan, Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	2.50%	2.60%