ALLOWANCE FOR LOAN AND LEASE LOSSES - Narrative (Details) - USD ($) $ in Millions |
9 Months Ended | ||||||
|---|---|---|---|---|---|---|---|
Sep. 04, 2026 |
Sep. 30, 2026 |
Jun. 30, 2026 |
Dec. 31, 2025 |
Sep. 30, 2025 |
Jun. 30, 2025 |
Dec. 31, 2024 |
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| Financing Receivable, Allowance for Credit Loss [Line Items] | |||||||
| Lease liabilities | $ 190 | $ 260 | |||||
| ALLL | 1,436 | $ 1,484 | $ 1,566 | $ 1,652 | $ 1,672 | $ 1,676 | |
| Decrease in the ALLL | $ 130 | ||||||
| BMO Bank | |||||||
| Financing Receivable, Allowance for Credit Loss [Line Items] | |||||||
| BMO PSL ALLL | $ 5 |
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- Definition Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of increase in allowance for credit loss for financing receivable from purchased seasoned loan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of increase (decrease) in allowance for credit loss on financing receivable. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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- Definition Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Details
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