| Standard label: | Unrealized Gain (Loss) on Investments |
| Name: | us-gaap:UnrealizedGainLossOnInvestments |
| Documentation: | The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period. |
| 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:UnrealizedGainLossOnInvestments |
| Label | Role | Language |
| Unrealized Gain (Loss) on Investments | http://www.xbrl.org/2003/role/label | en-US |
| Unrealized Gain (Loss) on Investments, Total | http://www.xbrl.org/2003/role/totalLabel | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 230 10 45 28 (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 230 |
| Part Of Roll Up: |
| us-gaap:GainLossOnInvestments |