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Pension and Postretirement Benefit Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2021
Benefit Plan Information
Defined benefit pension and postretirement plans adjustment	$ (121)	$ (47)	$ (240)	$ (155)
Qualified and Non-qualified Pension Benefits \| Funded
Benefit Plan Information
Company contributions year to date			83
Postretirement Benefits \| Funded
Benefit Plan Information
Company contributions year to date			2
Total Accumulated Other Comprehensive Income (Loss)
Benefit Plan Information
Defined benefit pension and postretirement plans adjustment	$ (121)	$ (47)	$ (240)	$ (155)
Forecast \| Pension and Postretirement Benefit Plans \| Funded \| Maximum
Benefit Plan Information
Estimated pension and postretirement employer contributions in current fiscal year					$ 200