Employee Benefits - Changes in APBO (Details) - Other Postretirement Benefit Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
PBO/APBO at beginning of year	$ 63	$ 69
Service cost	1	1	$ 1
Interest cost	2	2	3
Plan participants’ contributions	1	1
Actuarial losses (gains)	10	(6)
Benefit payments	(8)	(4)
PBO/APBO at end of year	$ 52	$ 63	$ 69