| Standard label: | Available-for-sale Securities, Amortized Cost Basis |
| Name: | us-gaap:AvailableForSaleSecuritiesAmortizedCost |
| Documentation: | This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Debit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:AvailableForSaleSecuritiesAmortizedCost |
| Label | Role | Language |
| Available-for-sale Securities, Amortized Cost Basis | http://www.xbrl.org/2003/role/label | en-US |
| Available-for-sale Securities, Amortized Cost Basis, Total | http://www.xbrl.org/2003/role/totalLabel | en-US |
| Reference | Role | Topic |