Investments (Concentrations of Credit Risk) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Investments in Japanese government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	$ 51,543	$ 55,418
Concentrations of credit risk at fair value	38,633	44,082
Investments in Brazilian government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	4,620	3,912
Concentrations of credit risk at fair value	3,921	3,413
Assets supporting experience-rated contractholder liabilities \| Investments in Japanese government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	537	536
Concentrations of credit risk at fair value	509	510
Short-term investments \| Investments in Brazilian government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	0	1
Concentrations of credit risk at fair value	0	1
Cash equivalents \| Investments in Brazilian government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	291	260
Concentrations of credit risk at fair value	291	260
Fixed maturities, available-for-sale \| Fixed maturities \| Investments in Japanese government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	50,988	54,863
Concentrations of credit risk at fair value	38,107	43,554
Fixed maturities, available-for-sale \| Fixed maturities \| Investments in Brazilian government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	4,329	3,651
Concentrations of credit risk at fair value	3,630	3,152
Fixed maturities, trading \| Fixed maturities \| Investments in Japanese government and government agency securities:
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Concentrations of credit risk at amortized cost	18	19
Concentrations of credit risk at fair value	$ 17	$ 18