cm:Concept: us-gaap:DebtSecuritiesHeldToMaturityMaturityRollingAfterTenYearsWeightedAverageYield
| Debt Securities, Held-to-maturity, Maturity, Rolling after Ten Years, Weighted Average Yield |
| us-gaap:DebtSecuritiesHeldToMaturityMaturityRollingAfterTenYearsWeightedAverageYield |
| Weighted average yield of investment in debt security measured at amortized cost (held-to-maturity), maturing after tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. |
| cm:Concept |
| Percent (num:percentItemType) |
| As Of (instant) |
| (no balance type) |
| false |
| us-gaap:DebtSecuritiesHeldToMaturityMaturityRollingAfterTenYearsWeightedAverageYield |