cm:Concept: us-gaap:ShareBasedGoodsAndNonemployeeServicesTransactionValuationMethodExpectedDividendRate
| Share-based Goods and Nonemployee Services Transaction, Valuation Method, Expected Dividend Rate |
| us-gaap:ShareBasedGoodsAndNonemployeeServicesTransactionValuationMethodExpectedDividendRate |
| The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the expected term of a nonvested share or option award issued to other than an employee. |
| cm:Concept |
| Percent (num:percentItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ShareBasedGoodsAndNonemployeeServicesTransactionValuationMethodExpectedDividendRate |