cm:Concept: us-gaap:DebtSecuritiesHeldToMaturityMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield
| Debt Securities, Held-to-maturity, Maturity, Rolling after One Through Five Years, Weighted Average Yield |
| us-gaap:DebtSecuritiesHeldToMaturityMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield |
| Weighted average yield of investment in debt security measured at amortized cost (held-to-maturity), maturing in second through fifth 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:DebtSecuritiesHeldToMaturityMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield |