cm:Level2TextBlock: us-gaap:GoodwillAndIntangibleAssetsGoodwillPolicy
| Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] |
| us-gaap:GoodwillAndIntangibleAssetsGoodwillPolicy |
| Disclosure of accounting policy for goodwill. This accounting policy also may address how an entity assesses and measures impairment of goodwill, how reporting units are determined, how goodwill is allocated to such units, and how the fair values of the reporting units are determined. |
| cm:Level2TextBlock |
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| us-gaap:GoodwillAndIntangibleAssetsGoodwillPolicy |