| Standard label: | Debt Securities, Held-to-maturity, Sold, Realized Gain (Loss) |
| Name: | us-gaap:HeldToMaturitySecuritiesSoldSecurityRealizedGainLoss |
| Documentation: | Amount of gain (loss) on sale of investment in debt security measured at amortized cost (held-to-maturity), including other-than-temporary impairment (OTTI). |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | For Period (duration) |
| Balance type: | Credit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:HeldToMaturitySecuritiesSoldSecurityRealizedGainLoss |
| Label | Role | Language |
| Debt Securities, Held-to-maturity, Sold, Realized Gain (Loss) | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 320 10 50 10 (c) | http://fasb.org/us-gaap/role/ref/legacyRef | 320 |
| Part Of Roll Up: |
| us-gaap:DebtSecuritiesRealizedGainLoss |