cm:Concept: us-gaap:AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLoss
| Accrual for Environmental Loss Contingencies, Foreign Currency Translation Gain (Loss) |
| us-gaap:AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLoss |
| Amount of foreign currency translation gain (loss) which decreases (increases) the accrual for environmental loss contingencies. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLoss |