v3.26.1
DEBT - Long-Term Debt (Details) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Debt Instrument    
Long-term debt, at fair value $ 307,566 $ 315,827
Trust preferred securities 1,600 1,600
Citigroup Inc.    
Debt Instrument    
Long-term debt, at fair value 171,000 177,855
Bank    
Debt Instrument    
Long-term debt, at fair value 31,544 36,481
Bank | Senior notes    
Debt Instrument    
Collateralized long-term advances from Federal Home Loan Bank 1,000 3,000
Broker-dealer and other    
Debt Instrument    
Long-term debt, at fair value $ 105,022 $ 101,491