| Standard label: | Underfunded Plan [Member] |
| Name: | us-gaap:UnderfundedPlanMember |
| Documentation: | Defined benefit plan in which retirement benefits are payable directly from plan assets segregated and restricted to provide such benefits and for which benefit obligation exceeds plan assets available to provide retirement benefits. |
| 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:UnderfundedPlanMember |
| Label | Role | Language |
| Underfunded Plan [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 715 20 50 2 | http://fasb.org/us-gaap/role/ref/legacyRef | 715 |