Fair Value Measurements - Gains or losses recorded related to fair value option (Details) - Fair Value Option - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 719	$ (373)	$ 1,704
Other bond securities
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	382	(822)	(12)
Alternative investments
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	334	224	1,650
Long-term debt
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 3	$ 225	$ 66