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, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
FVA at beginning of year	$ 52	$ 50
Employer contributions	0	0
Plan participants’ contributions	1	1
Benefit payments	(4)	(8)
Actual return on plan assets	(2)	9
FVA at end of year	$ 47	$ 52