| Standard label: | Other Postretirement Benefits Plan [Member] |
| Name: | us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember |
| Documentation: | Plan designed to provide other postretirement benefits. Includes, but is not limited to, defined benefit and defined contribution plans. Excludes pension 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:OtherPostretirementBenefitPlansDefinedBenefitMember |
| Label | Role | Language |
| Other Postretirement Benefits Plan [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 712 10 15 4 (d) | http://fasb.org/us-gaap/role/ref/legacyRef | 712 |
| FASB Accounting Standards Codification 715 20 50 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 715 |
| FASB Accounting Standards Codification 715 20 50 2 | http://fasb.org/us-gaap/role/ref/legacyRef | 715 |
| FASB Accounting Standards Codification 715 70 50 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 715 |