Postretirement Benefit Plans (Weighted-Average Asset Allocation By Investment Category) (Details) - Defined Benefit Pension Plan [Member]	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	100.00%
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	50.44%
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	38.14%
Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	11.42%