Postretirement Benefit Plans (Rollforward of Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in benefit obligation:
Benefit obligation at beginning of year	$ 1,199
Benefit obligation at end of year	1,085	$ 1,199
Other postretirement benefit plans
Change in benefit obligation:
Benefit obligation at beginning of year	44	49
Interest cost	1	2	$ 2
Benefits paid	(3)	(3)
Actuarial gain	0	1
Plan Amendment and other	0	(5)
Benefit obligation at end of year	$ 42	$ 44	$ 49