Investments - Schedule of Maturities for Fixed Income Securities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Amortized cost, net
Due in one year or less	$ 1,941	$ 1,544
Due after one year through five years	22,197	22,889
Due after five years through ten years	20,443	17,431
Due after ten years	9,073	10,526
Subtotal	53,654	52,390
ABS and MBS	3,078	1,226
Amortized cost, net	56,732	53,616
Fair value
Due in one year or less	1,929	1,531
Due after one year through five years	22,331	22,595
Due after five years through ten years	20,699	17,130
Due after ten years	9,107	10,250
Subtotal	54,066	51,506
ABS and MBS	3,120	1,241
Fair value	$ 57,186	$ 52,747