cm:Concept: us-gaap:DebtSecuritiesAvailableForSaleMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield
| Debt Securities, Available-for-sale, Maturity, Rolling after Five Through Ten Years, Weighted Average Yield |
| us-gaap:DebtSecuritiesAvailableForSaleMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield |
| Weighted average yield of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in sixth through tenth rolling 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:DebtSecuritiesAvailableForSaleMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield |