Benefit Plans (Narrative) (Details) - USD ($)		6 Months Ended
	May 31, 2021	Jun. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Decrease in accrued postretirement health care cost liability	$ 432,000,000
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, contributions by employer		$ 6,000,000
Pension [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions		25,000,000
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