Other Comprehensive Income (Loss) - Amounts reclassified from accumulated other comprehensive income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for credit losses	$ 6	$ 0	$ 4	$ (23)
Income (loss) before income taxes and income (loss) from operating affiliates	1,050	741	3,537	2,197
Income tax (expense) benefit	(98)	(72)	(296)	(203)
Net of tax	988	723	3,377	2,109
Reclassification out of accumulated other comprehensive income | Unrealized appreciation (decline) on available-for-sale investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses)	54	(104)	(38)	(345)
Provision for credit losses	6	0	4	(23)
Income (loss) before income taxes and income (loss) from operating affiliates	60	(104)	(34)	(368)
Income tax (expense) benefit	0	8	12	24
Net of tax	$ 60	$ (96)	$ (22)	$ (344)