Pension - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Non-Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Plan assets		$ 0
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Market-related valuation of pension plan assets		4,400,000,000
Plan assets		4,846,000,000	$ 4,623,000,000	$ 4,441,000,000
Increase in pension liability due to litigation settlement	$ 142,000,000	0	0	$ 142,000,000
Plan assets invested in separate accounts of subsidiaries		4,500,000,000
Plan assets invested in funds offered by an unaffiliated insurance company		300,000,000
Pension Plan | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets		$ 2,501,000,000	2,122,000,000
Target allocation percentages		58.00%
Pension Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets		$ 1,147,000,000	$ 1,449,000,000
Target allocation percentages		25.00%
Pension Plan | Other Plan Asset Categories
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentages		17.00%
Pension Plan | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions for 2022