cm:Member: us-gaap:AccumulatedOtherthanTemporaryImpairmentIncludingPortionAttributableToNoncontrollingInterestMember
| Accumulated Other-than-Temporary Impairment Including Portion Attributable to Noncontrolling Interest [Member] |
| us-gaap:AccumulatedOtherthanTemporaryImpairmentIncludingPortionAttributableToNoncontrollingInterestMember |
| Accumulated other comprehensive loss resulting from other-than-temporary impairments (OTTI) of debt securities if a portion of an other-than-temporary impairment has not been recognized in earnings, including the portion attributable to the noncontrolling interest. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:AccumulatedOtherthanTemporaryImpairmentIncludingPortionAttributableToNoncontrollingInterestMember |