Benefit Plans (Narrative) (Details)	9 Months Ended
	Sep. 30, 2020 USD ($)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, contributions by employer	$ 16,000,000
Pension [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	20,000,000
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, contributions by employer	0
Postretirement [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	$ 60,000,000