Inventories (Details) - USD ($) $ in Thousands  | 
Dec. 31, 2021  | 
Dec. 31, 2020  | 
|---|---|---|
| Inventories | ||
| Finished goods | $ 50,416 | $ 39,496 | 
| Work-in-process | 8,916 | 8,253 | 
| Raw material and supplies | 44,687 | 31,733 | 
| Inventories | 104,019 | 79,482 | 
| Inventories - truck chassis floor plan | $ 2,655 | $ 8,146 | 
| X | ||||||||||
- Definition Amount of inventory, truck chassis floor plan expected to be sold, or consumed within one year or operating cycle, if longer. No definition available. 
  | 
| X | ||||||||||
- References No definition available. 
  | 
| X | ||||||||||
- Definition Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
  | 
| X | ||||||||||
- Definition Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
  | 
| X | ||||||||||
- Definition Aggregated amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed. This amount is net of valuation reserves and adjustments. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
  | 
| X | ||||||||||
- Definition Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
  |