Benefit Plans, Plans With Projected and Accumulated Benefit Obligations in Excess of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Additional Information [Abstract]
Accumulated benefit obligation for all defined benefit pension plans	$ 3,200	$ 3,100
Actuarial loss	236	300
Future capital calls from various third party limited partnership investments	$ 192
Defined Benefit Plan, Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan, Additional Information [Abstract]
Target allocation of plan assets invested in equity securities and limited partnerships	40.00%
Defined Benefit Plan, Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan, Additional Information [Abstract]
Target allocation of plan assets invested in equity securities and limited partnerships	60.00%
Pension Benefits [Member]
Information for Plans with Projected and Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 3,103	3,021
Accumulated benefit obligation	3,096	3,014
Fair value of plan assets	2,596	2,456
Defined Benefit Plan, Additional Information [Abstract]
Actuarial loss	(236)	(299)
Other Postretirement Benefits [Member]
Information for Plans with Projected and Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	16	16
Defined Benefit Plan, Additional Information [Abstract]
Actuarial loss	$ (3)	$ (3)