| Standard label: | Internal Investment Grade [Member] |
| Name: | us-gaap:InternalInvestmentGradeMember |
| Documentation: | Credit rating classification developed by the entity in which the probability of default is low and full and timely repayments are expected. |
| Object type: | cm:Member |
| Data type: | [Member] (nonnum:domainItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | true |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:InternalInvestmentGradeMember |
| Label | Role | Language |
| Internal Investment Grade [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 326 20 50 5 | http://www.xbrl.org/2009/role/commonPracticeRef | 326 |