| Segment Reporting, Reconciliation of Revenue by Segment to Consolidated [Table Text Block] |
| | | Three Months Ended June 30, | | | Six Months Ended June 30, | |
| | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| | | Amount | | | % | | | Amount | | | % | | | Amount | | | % | | | Amount | | | % | |
| | | (in thousands) | |
| Truckload Services revenue | | $ | 86,074 | | | | 62.9 | | | $ | 92,824 | | | | 69.4 | | | $ | 164,331 | | | | 63.3 | | | $ | 185,253 | | | | 68.5 | |
| Brokerage and Logistics Services revenue | | | 50,820 | | | | 37.1 | | | | 40,982 | | | | 30.6 | | | | 95,225 | | | | 36.7 | | | | 85,253 | | | | 31.5 | |
| Total revenues | | $ | 136,894 | | | | 100.0 | | | $ | 133,806 | | | | 100.0 | | | $ | 259,556 | | | | 100.0 | | | $ | 270,506 | | | | 100.0 | |
| | | Three Months Ended June 30, | | | Six Months Ended June 30, | |
| | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| | | Amount | | | % | | | Amount | | | % | | | Amount | | | % | | | Amount | | | % | |
| | | (in thousands, except percentage data) | |
| United States - domestic shipments | | $ | 93,570 | | | | 56.8 | | | $ | 84,304 | | | | 55.8 | | | $ | 172,954 | | | | 56.4 | | | $ | 168,148 | | | | 54.9 | |
| Shipments to or from Mexico | | $ | 70,843 | | | | 43.0 | | | $ | 66,537 | | | | 44.0 | | | $ | 133,017 | | | | 43.4 | | | $ | 137,634 | | | | 44.9 | |
| Shipments to or from Canada | | $ | 239 | | | | 0.2 | | | $ | 293 | | | | 0.2 | | | $ | 561 | | | | 0.2 | | | $ | 693 | | | | 0.2 | |
| Total | | $ | 164,652 | | | | 100.0 | | | $ | 151,134 | | | | 100.0 | | | $ | 306,532 | | | | 100.0 | | | $ | 306,475 | | | | 100.0 | |
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