| Standard label: | Restricted Investments, at Fair Value |
| Name: | us-gaap:RestrictedInvestmentsAtFairValue |
| Documentation: | The aggregate value of all restricted investments. |
| 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:RestrictedInvestmentsAtFairValue |
| Label | Role | Language |
| Restricted Investments, at Fair Value | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 946 320 S99 1 (SX 210.12-12.6(c)) | http://fasb.org/us-gaap/role/ref/legacyRef | 946 |
| FASB Accounting Standards Codification 946 320 S99 4 (SX 210.12-12C.9(c)) | http://fasb.org/us-gaap/role/ref/legacyRef | 946 |