| Standard label: | Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost |
| Name: | us-gaap:AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis |
| Documentation: | Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Debit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis |
| Label | Role | Language |
| Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost | http://www.xbrl.org/2003/role/label | en-US |
| Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost, Total | http://www.xbrl.org/2003/role/totalLabel | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 320 10 50 2 (d) | http://fasb.org/us-gaap/role/ref/legacyRef | 320 |
| FASB Accounting Standards Codification 320 10 50 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 320 |
| FASB Accounting Standards Codification 942 320 50 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 942 |
| Part Of Roll Up: |
| us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis |