EBPs Obligation Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	$ 1,319	$ 1,466
Service cost	50	50	$ 54
Interest cost	46	59	62
Plan participants’ contributions	0	0
Benefits paid	(35)	(35)
Net actuarial loss (gain)	(90)	40
Settlements	(103)	(261)
Net increase (decrease) in benefit obligation	(132)	(147)
Benefit obligation at end of year	1,187	1,319	1,466
Other Postretirement Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	206	197
Service cost	1	1	1
Interest cost	7	8	8
Plan participants’ contributions	2	3
Benefits paid	(13)	(14)
Net actuarial loss (gain)	(17)	11
Settlements	0	0
Net increase (decrease) in benefit obligation	(20)	9
Benefit obligation at end of year	$ 186	$ 206	$ 197