Pension and Postretirement Benefit Plans - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Qualified and Non-qualified Pension Benefits
Benefit Plan Information
Company contributions year to date	$ 118
Postretirement Benefits
Benefit Plan Information
Company contributions year to date	3
Pension and Postretirement Benefit Plans | Maximum
Benefit Plan Information
Estimated pension and postretirement employer contributions in current fiscal year	$ 200