cm:Concept: us-gaap:RetainedEarningsEffectiveDatesOfNewRetainedEarningsAccountEstablishedAfterReadjustment
| Retained Earnings, Effective Date of New Retained Earnings Account Established after Readjustment |
| us-gaap:RetainedEarningsEffectiveDatesOfNewRetainedEarningsAccountEstablishedAfterReadjustment |
| Effective date of a new retained earnings account established after a readjustment (for example, but not limited to, quasi-reorganization), in CCYY-MM-DD format. |
| cm:Concept |
| Date (xbrli:dateItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:RetainedEarningsEffectiveDatesOfNewRetainedEarningsAccountEstablishedAfterReadjustment |