| Standard label: | Investment Building and Building Improvements |
| Name: | us-gaap:InvestmentBuildingAndBuildingImprovements |
| Documentation: | Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements. |
| 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:InvestmentBuildingAndBuildingImprovements |
| Label | Role | Language |
| Investment Building and Building Improvements | http://www.xbrl.org/2003/role/label | en-US |
| Investment Building and Building Improvements, Total | http://www.xbrl.org/2003/role/totalLabel | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 944 210 S99 1 (SX 210.7-03.1(d)) | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |