| Document and Entity Information Document | Aug. 14, 2024 |
| Cover [Abstract] | |
| Document type | 8-K |
| Document period end date | Aug. 14, 2024 |
| Entity registrant name | DISCOVER FINANCIAL SERVICES |
| Entity file number | 001-33378 |
| Entity incorporation, state or country code | DE |
| Entity tax identification number | 36-2517428 |
| Entity address, address line one | 2500 Lake Cook Road |
| Entity address, city or town | Riverwoods |
| Entity address, state or province | IL |
| Entity address, postal zip code | 60015 |
| City area code | 224 |
| Local phone number | 405-0900 |
| Written communications | false |
| Soliciting material | false |
| Pre-commencement tender offer | false |
| Pre-commencement issuer tender offer | false |
| Title of 12(b) security | Common Stock, par value $0.01 per share |
| Trading symbol | DFS |
| Security exchange name | NYSE |
| Entity emerging growth company | false |
| Entity central index key | 0001393612 |
| Amendment flag | false |
