cm:Concept: us-gaap:DebtSecuritiesHeldToMaturityTransferDerivativeHedgeGainLoss
| Debt Securities, Held-to-maturity, Transfer, Derivative Hedge, Gain (Loss) |
| us-gaap:DebtSecuritiesHeldToMaturityTransferDerivativeHedgeGainLoss |
| Amount of gain (loss) in accumulated other comprehensive income (AOCI) of derivative hedging forecasted acquisition of investment in debt security measured at amortized cost (held-to-maturity), transferred to investment in debt security measured at fair value with changes in fair value recognized in other comprehensive income (available-for-sale) and net income (trading). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:DebtSecuritiesHeldToMaturityTransferDerivativeHedgeGainLoss |