cm:Concept: us-gaap:OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus
| Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Change in Status |
| us-gaap:OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus |
| This item represents reductions in the amount of cumulative losses recognized in earnings for other than temporary impairments (OTTI) for which a portion of the impairment had been recognized in other comprehensive income (a component of shareholders' equity) due to a change in status of the impaired security because of a change in the entity's intent to either sell the impaired security or it has become more likely than not that the entity will be required to sell the security before recovery of its cost basis. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus |