| Standard label: | Accumulated Other-than-Temporary Impairment Attributable to Parent [Member] |
| Name: | us-gaap:AccumulatedOtherThanTemporaryImpairmentMember |
| Documentation: | Accumulated other comprehensive loss resulting from other-than-temporary impairments (OTTI) of debt securities if a portion of an other-than-temporary impairment has not been recognized in earnings, attributable to the parent. |
| Object type: | cm:Member |
| Data type: | [Member] (nonnum:domainItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | true |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:AccumulatedOtherThanTemporaryImpairmentMember |
| Label | Role | Language |
| Accumulated Other-than-Temporary Impairment Attributable to Parent [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 220 10 45 14A | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 220 10 45 10A (g) | http://fasb.org/us-gaap/role/ref/legacyRef | 220 |
| FASB Accounting Standards Codification 220 10 45 17B | http://www.xbrl.org/2003/role/disclosureRef | 220 |
| FASB Accounting Standards Codification 320 10 45 9A | http://fasb.org/us-gaap/role/ref/legacyRef | 320 |
| FASB Accounting Standards Codification 810 10 50 1A (c),(3) | http://fasb.org/us-gaap/role/ref/legacyRef | 810 |