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Summary of Significant Accounting Policies - Additional Information (Details)
$ in Billions
6 Months Ended
Jun. 30, 2025
segment
May 18, 2025
USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Number of operating segments | segment 3  
Discover    
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Business combination, allowance for credit losses PCD loan | $   $ 8.8