Consolidated Statements of Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Truckload services, related party amounts	$ 660	$ 947	$ 1,636
Purchased transportation and equipment rent [Member]
Operating expenses, related party amounts	1,695	22	65
Direct personnel and related benefits [Member]
Operating expenses, related party amounts	42,371	27,532	31,932
Operating supplies and expenses [Member]
Operating expenses, related party amounts	3,887	826	895
Occupancy expense [Member]
Operating expenses, related party amounts	12,384	12,925	11,794
General and administrative expense [Member]
Operating expenses, related party amounts	8,923	5,688	7,633
Insurance and claims [Member]
Operating expenses, related party amounts	$ 17,997	$ 16,542	$ 17,570