Employee Benefits - Change in FVA (Other Post Retirement Benefit Plan Assets) (Details) - Other Postretirement Benefit Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
FVA at beginning of year	$ 52	$ 47
Employer contributions	0	0
Plan participants’ contributions	1	1
Benefit payments	(11)	(8)
Actual return on plan assets	10	12
FVA at end of year	$ 52	$ 52