Accumulated Other Comprehensive Income (Loss) - After-tax Changes by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (190)	$ (160)	$ (184)	$ (163)
Amounts arising during the period	(3)	(4)	(10)	(1)
Reclassifications from AOCI	0	1	1	1
Net OCI during the period	(3)	(3)	(9)	0
Balance at end of period	(193)	(163)	(193)	(163)
Other Comprehensive Income (Loss), Equity Investees' AOCI, reclassification, After Tax	0	0	0	0
Other Comprehensive Income (Loss), Equity Investees' AOCI, before Reclassifications, Net of Tax	0	0	0	1
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(3)	(4)	(3)	(4)
Net OCI during the period	0	0	0	0
Balance at end of period	(3)	(4)	(3)	(4)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(202)	(167)	(194)	(168)
Net OCI during the period	(4)	(5)	(12)	(4)
Balance at end of period	(206)	(172)	(206)	(172)
Equity Investees' OCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	4	4	4	3
Net OCI during the period	0	0	0	1
Balance at end of period	4	4	4	4
Unrealized gains (losses) on qualifying derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	11	7	9	6
Net OCI during the period	1	2	3	3
Balance at end of period	$ 12	$ 9	$ 12	$ 9