Fair Value Measurements - Fair Value Disclosures for Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions |
Mar. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|
| Fair Value | Significant Other Observable Inputs (Level 2) | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long-term debt, including current maturities, excluding finance leases | $ 29,806 | $ 28,033 |
| Fair Value | Significant Unobservable Inputs (Level 3) | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Commercial mortgage loans, including assets held for sale | 1,451 | 1,430 |
| Carrying Value | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long-term debt, including current maturities, excluding finance leases | 31,783 | 29,585 |
| Commercial mortgage loans, including assets held for sale | $ 1,562 | $ 1,533 |