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Business Combinations and Discontinued Operations - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	May 18, 2025	Dec. 31, 2025	Dec. 31, 2024
Business Combination [Line Items]
Weighted Average Remaining Amortization Period		10 years 3 months 18 days	6 years
Purchased credit card relationships
Business Combination [Line Items]
Weighted Average Remaining Amortization Period		10 years 3 months 18 days	6 years 1 month 6 days
Network and financial partner relationships
Business Combination [Line Items]
Weighted Average Remaining Amortization Period		10 years 7 months 6 days
Core deposit
Business Combination [Line Items]
Weighted Average Remaining Amortization Period		9 years 4 months 24 days
Discover
Business Combination [Line Items]
Intangible assets with definite lives	$ 12,700
Intangible assets with indefinite lives	4,970
Total	$ 17,670
Acquired finite-lived intangible assets, weighted average useful life	11 years
Discover \| Discover Network
Business Combination [Line Items]
Intangible assets with indefinite lives	$ 2,700
Discover \| Brand/Trade names
Business Combination [Line Items]
Intangible assets with indefinite lives	$ 2,270
Discover \| Purchased credit card relationships
Business Combination [Line Items]
Weighted Average Remaining Amortization Period	11 months
Intangible assets with definite lives	$ 10,100
Discover \| Network and financial partner relationships
Business Combination [Line Items]
Weighted Average Remaining Amortization Period	11 months
Intangible assets with definite lives	$ 1,500
Discover \| Core deposit
Business Combination [Line Items]
Weighted Average Remaining Amortization Period	10 months
Intangible assets with definite lives	$ 1,100