| Standard label: | External Credit Rating, Investment Grade [Member] |
| Name: | us-gaap:ExternalCreditRatingInvestmentGradeMember |
| Documentation: | External credit-rating that could be used to describe the current status of the payment and performance risk of credit derivatives and guarantee obligations that connote investment grade. |
| 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:ExternalCreditRatingInvestmentGradeMember |
| Label | Role | Language |
| External Credit Rating, Investment Grade [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 460 10 50 4 (a) | http://fasb.org/us-gaap/role/ref/legacyRef | 460 |
| FASB Accounting Standards Codification 815 10 50 4K (a) | http://fasb.org/us-gaap/role/ref/legacyRef | 815 |