Fair Value Measurements - Gains or losses recorded related to fair value option (Details) - Fair Value Option - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 44	$ (229)	$ 392	$ (501)
Other bond securities
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	(38)	(241)	97	(915)
Alternative investments
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	76	(57)	287	174
Long-term debt
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 6	$ 69	$ 8	$ 240