| Standard label: | Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax |
| Name: | us-gaap:AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax |
| Documentation: | Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Credit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax |
| Label | Role | Language |
| Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | http://www.xbrl.org/2003/role/label | en-US |
| Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax, Total | http://www.xbrl.org/2003/role/totalLabel | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 320 10 50 2 (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 320 |