cm:Concept: us-gaap:PresentValueOfFutureInsuranceProfitsForeignCurrencyTranslationGainLoss
| Present Value of Future Insurance Profits, Foreign Currency Translation Gain (Loss) |
| us-gaap:PresentValueOfFutureInsuranceProfitsForeignCurrencyTranslationGainLoss |
| Amount of foreign currency translation gain (loss) which increases (decreases) present value of future profits of insurance contract acquired in business combination. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:PresentValueOfFutureInsuranceProfitsForeignCurrencyTranslationGainLoss |