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BUSINESS COMBINATIONS - Narrative (Details) $ / shares in Units, $ in Millions |  |  |  | 12 Months Ended
--- | --- | --- | --- | ---
Apr. 04, 2023 USD ($) | Mar. 27, 2023 USD ($) $ / shares shares | Jan. 03, 2022 $ / shares shares | Dec. 31, 2024 USD ($) $ / shares | Dec. 31, 2023 USD ($) $ / shares | Dec. 31, 2022 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |
Net interest income |  |  |  | $ 7,143 | $ 6,712 | $ 2,946
Noninterest income |  |  |  | 2,615 | 12,075 | 2,136
Net income |  |  |  | 2,777 | 11,466 | 1,098
Gain on acquisition |  |  |  | $ 0 | $ 9,808 | 431
Class A |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  |  | $ 1 | $ 1 |
CIT Group Inc. |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  | $ 0.01 |  |  |
FDIC Credit Facility |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
FDIC advances, maximum amount available |  | $ 70,000 |  |  |  |
Purchase Money Note |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Debt instrument, term |  | 5 years |  |  |  |
Principal amount |  | $ 36,070 |  |  |  |
Notes payable, fair value disclosure |  | 35,810 |  |  |  |
SVBB |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Total assets acquired |  | 107,539 |  |  |  |
Loans and leases, net of the initial PCD ALLL |  | 68,468 |  |  |  |
Cash and interest-earning deposits at banks |  | 35,310 |  |  |  |
Total liabilities assumed |  | 61,423 |  |  |  |
Deposits |  | 56,014 |  |  |  |
Assets acquired, discount |  | 16,450 |  |  |  |
Business combination, financing receivable acquired, amount covered by share-loss agreement |  | $ 60,000 |  |  |  |
Business combination, financing receivable acquired, amount covered by share-loss agreement, coverage percentage for loss up to $5 billion |  | 0.00% |  |  |  |
Business combination, financing receivable acquired, amount covered by share-loss agreement, coverage percentage for loss in excess of $5 billion |  | $ 5,000 |  |  |  |
Business combination, financing receivable acquired, above threshold amount covered by share-loss agreement, percentage |  | 50.00% |  |  |  |
Share-Loss Agreement, reimbursement percentage |  | 50.00% |  |  |  |
Share-Loss Agreement, term |  | 5 years |  |  |  |
Share-Loss Agreement, reimbursement term |  | 8 years |  |  |  |
Loans funded after acquisition date, loss share term |  | 1 year |  |  |  |
Share-Loss Agreement, true-up payment term |  | 45 days |  |  |  |
True-up amount |  | $ 1,500 |  |  |  |
Cash settled value appreciation instrument issued and issuable (in shares) | shares |  | 5,000,000 |  |  |  |
Cash settled value appreciation instrument issued and issuable, number of shares benchmark (in shares) | shares |  | 1 |  |  |  |
Number of trading days |  | 2 days |  |  |  |
Cash settled value appreciation instrument, threshold amount (in dollars per share) | $ / shares |  | $ 582.55 |  |  |  |
Cash settled value appreciation instrument, maximum amount |  | $ 500 |  |  |  |
Payment to acquire business, value appreciation instrument exercised | $ 500 |  |  |  |  |
Gain on acquisition, after income taxes |  | 9,808 |  |  | $ 9,810 |
Deferred tax liabilities |  | 3,364 |  |  | 3,360 |
UPB |  | 71,287 |  |  |  |
Purchase accounting adjustment of discount |  | 2,300 |  |  |  |
Net interest income |  |  |  |  | 1,950 |
Noninterest income |  |  |  |  | 478 |
Net income |  |  |  |  | $ 530 |
Gain on acquisition |  | 13,172 |  |  |  |
SVBB | Non-PCD |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Loans and leases acquired, FV |  | 66,420 |  |  |  |
UPB |  | $ 68,719 |  |  |  |
SVBB | FDIC Credit Facility |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
FHLB, advances, interest rate |  | 0.00% |  |  |  |
SVBB | Secured Debt | FDIC Credit Facility |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Basis spread on variable rate |  | 0.25% |  |  |  |
SVBB | Purchase Money Note |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Debt instrument, term |  | 5 years |  |  |  |
Debt instrument, face amount |  | $ 35,000 |  |  |  |
SVBB | Purchase Money Note | Secured Debt |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Debt instrument, stated interest rate |  | 3.50% |  |  |  |
CIT Group Inc. |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Gain on acquisition |  |  |  |  |  | $ 431
CIT Group Inc. | Class A |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Common stock, terms of conversion, conversion ratio |  |  | 0.062 |  |  |
Business acquisition, equity interest Issued or issuable (in shares) | shares |  |  | 6,100,000 |  |  |

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