Accumulated Other Comprehensive Income - Components in Accumulated Other Comprehensive Income (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]
Net (loss) on securities	$ 0	$ (1)	$ (1)	$ (2)
Income tax expense (benefit)	61	53	141	164
Net income (loss)	207	152	2,626	478
Interest expense	630	183	1,707	394
General and administrative	$ 184	$ 31	496	$ 95
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense (benefit)			0
General and administrative			(2)
Reclassifications, net of tax			(2)
Past service liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
General and administrative			0
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
General and administrative			(2)
Reclassification from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)			12
Reclassification from AOCI | Unrealized gains on available-for-sale securities:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net (loss) on securities			0
Income tax expense (benefit)			0
Net income (loss)			0
Reclassification from AOCI | Unrealized gains on cash flow hedges:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense (benefit)			(5)
Net income (loss)			14
Interest expense			$ 19