Fair Value Measurements - Gains or Losses Recorded Related to Fair Value Option (Details) - Fair Value Option - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 98	$ 43	$ 180	$ 139
Other bond securities
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	5	(11)	7	9
Alternative investments
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	28	54	108	130
All other investments
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 65	$ 0	$ 65	$ 0