| Standard label: | Debt Securities, Gain (Loss), Excluding OTTI |
| Name: | us-gaap:DebtSecuritiesGainLossExcludingOtti |
| Documentation: | Amount of unrealized and realized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity), investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and investment in debt security measured at fair value with change in fair value recognized in net income (trading). Excludes 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:DebtSecuritiesGainLossExcludingOtti |
| Label | Role | Language |
| Debt Securities, Gain (Loss), Excluding OTTI | http://www.xbrl.org/2003/role/label | en-US |
| Debt Securities, Gain (Loss), Excluding OTTI, Total | http://www.xbrl.org/2003/role/totalLabel | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 220 10 S99 2 (SX 210.5-03(7)(c)) | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 220 10 S99 2 (SX 210.5-03(9)(a)) | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 942 220 S99 1 (SX 210.9-04(13)(g)) | http://fasb.org/us-gaap/role/ref/legacyRef | 942 |
| FASB Accounting Standards Codification 944 220 S99 1 (SX 210.7-04(3)(d)) | http://www.xbrl.org/2003/role/disclosureRef | 944 |