Benefit Plans (Narrative) (Details)	3 Months Ended
	Mar. 31, 2021 USD ($)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, contributions by employer	$ 3,000,000
Pension [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	30,000,000
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