cm:Concept: us-gaap:RefundReceivedRelatedToRevenueFromDifferentYearYearRevenueRecognized
| Refund Received Related to Revenue from Different Year, Year Revenue Recognized |
| us-gaap:RefundReceivedRelatedToRevenueFromDifferentYearYearRevenueRecognized |
| Discloses year revenue was initially recognized related to refunds that are recognized in a period other than the period in which the related revenue was recognized and that have a material effect on net income. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:RefundReceivedRelatedToRevenueFromDifferentYearYearRevenueRecognized |