| Standard label: | Merchant Marine, Operating-differential Subsidy |
| Name: | us-gaap:MerchantMarineOperatingDifferentialSubsidy |
| Documentation: | Amount of operating-differential subsidy received pursuant to Merchant Marine Act of 1936. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | For Period (duration) |
| Balance type: | Credit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:MerchantMarineOperatingDifferentialSubsidy |
| Label | Role | Language |
| Merchant Marine, Operating-differential Subsidy | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 220 10 S99 7 (SAB Topic 11.A) | http://www.xbrl.org/2003/role/disclosureRef | 220 |
| Part Of Roll Up: |
| us-gaap:CostOfRevenue |