v3.24.4
Document and Entity Information Document - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 13, 2024
Dec. 31, 2022
Cover [Abstract]      
Document type 10-K/A    
Document annual report true    
Document period end date Dec. 31, 2023    
Document transition report false    
Entity file number 001-33378    
Entity registrant name DISCOVER FINANCIAL SERVICES    
Entity incorporation, state 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    
Entity phone number, city area code 224    
Entity phone number, local phone number 405-0900    
Title of 12(b) security Common Stock, par value $0.01 per share    
Trading symbol DFS    
Security exchange name NYSE    
Entity well-known seasoned issuer Yes    
Entity voluntary filers No    
Entity current reporting status No    
Entity interactive data current Yes    
Entity filer category Large Accelerated Filer    
Smaller reporting company false    
Emerging growth company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] true    
Document Financial Statement Restatement Recovery Analysis [Flag] true    
Entity shell company false    
Entity public float $ 29,097,770,033    
Entity common stock, shares outstanding   251,226,920  
Common Stock, par or stated value per share $ 0.01   $ 0.01
Entity central index key 0001393612    
Current fiscal year end date --12-31    
Document fiscal year focus 2023    
Document fiscal period focus FY    
Amendment flag true    
Auditor Name Deloitte & Touche LLP    
Auditor Location Chicago, Illinois    
Auditor Firm ID 34