Investments (Concentrations of Credit Risk) (Details) - Foreign government - USD ($) $ in Millions |
Mar. 31, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Japan | ||
| Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] | ||
| Fair Value, Concentration of Risk, Investments | $ 15,609 | $ 16,265 |
| Republic of Korea | ||
| Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] | ||
| Fair Value, Concentration of Risk, Investments | 4,982 | 5,971 |
| Mexico | ||
| Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] | ||
| Fair Value, Concentration of Risk, Investments | $ 4,709 | $ 4,190 |