| Standard label: | Schedule of Assumptions for Long-Duration Contracts by Product and Guarantee [Table Text Block] |
| Name: | us-gaap:ScheduleOfAssumptionsForLongDurationContractsByProductAndGuaranteeTextBlock |
| Documentation: | Tabular disclosure of the underlying assumptions and percentages or rates used in determining the fair value of guarantee obligations for each type of long-duration contract. |
| Object type: | cm:Level3TextBlock |
| Data type: | Text Block (HTML) (nonnum:textBlockItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:ScheduleOfAssumptionsForLongDurationContractsByProductAndGuaranteeTextBlock |
| Label | Role | Language |
| Schedule of Assumptions for Long-Duration Contracts by Product and Guarantee [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 944 20 55 15 | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |
| FASB Accounting Standards Codification 944 30 50 2 | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |
| FASB Accounting Standards Codification 944 40 50 6 | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |
| FASB Accounting Standards Codification 944 40 50 7 | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |
| FASB Accounting Standards Codification 944 40 50 8 | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |
| FASB Accounting Standards Codification 944 80 50 1 (c) | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |