cm:Concept: us-gaap:DeferredTaxesBusinessCombinationValuationAllowanceAvailableToReduceIncomeTaxExpense
| Deferred Taxes, Business Combination, Valuation Allowance, Available to Reduce Income Tax Expense |
| us-gaap:DeferredTaxesBusinessCombinationValuationAllowanceAvailableToReduceIncomeTaxExpense |
| The amount of the valuation allowance recorded in a business combination against deductible temporary differences for which related tax benefits will be recorded as a reduction of the acquired entity's income tax expense (after such benefits are first being applied to reduce goodwill and then other noncurrent intangible assets to zero). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:DeferredTaxesBusinessCombinationValuationAllowanceAvailableToReduceIncomeTaxExpense |