Other Expense (Schedule of Other Expense) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | 12 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2023 |
Sep. 30, 2023 |
Dec. 31, 2022 |
Sep. 30, 2022 |
Sep. 30, 2023 |
Sep. 30, 2022 |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
|
| Component of Other Expense [Abstract] | |||||||||
| Fraud losses and other charges | $ 131 | $ 149 | $ 92 | ||||||
| Postage | 115 | 97 | 91 | ||||||
| Credit-related inquiry fees | 40 | 31 | 24 | ||||||
| Supplies | 38 | 35 | 46 | ||||||
| Impairment charges | 0 | 0 | 95 | ||||||
| Other expense | 479 | 228 | 272 | ||||||
| Total other expense | $ 263 | $ 254 | $ 154 | $ 154 | $ 540 | $ 386 | $ 803 | $ 540 | $ 620 |