Accumulated Other Comprehensive Income (Loss) - After-tax Changes by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (137)	$ (124)	$ (124)	$ (157)
Amounts arising during the period	(6)	(10)	(20)	12
Reclassifications from AOCI	1	4	2	15
Net OCI during the period	(5)	(6)	(18)	27
Balance at end of period	(142)	(130)	(142)	(130)
Unrealized gains (losses) on qualifying derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	4	2	3	1
Amounts arising during the period	0	0	0	0
Reclassifications from AOCI	1	0	2	1
Net OCI during the period	1	0	2	1
Balance at end of period	5	2	5	2
Defined benefit plans Prior service costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(4)	(6)	(5)	(6)
Amounts arising during the period	0	0	0	(1)
Reclassifications from AOCI	0	1	1	2
Net OCI during the period	0	1	1	1
Balance at end of period	(4)	(5)	(4)	(5)
Defined benefit plans Actuarial gain (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(140)	(122)	(124)	(152)
Amounts arising during the period	(6)	(10)	(21)	11
Reclassifications from AOCI	0	3	(1)	12
Net OCI during the period	(6)	(7)	(22)	23
Balance at end of period	(146)	(129)	(146)	(129)
Equity Investees' OCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	3	2	2	0
Amounts arising during the period	0	0	1	2
Reclassifications from AOCI	0	0	0	0
Net OCI during the period	0	0	1	2
Balance at end of period	$ 3	$ 2	$ 3	$ 2