Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating revenues:
Total operating revenues	$ 1,750,980	$ 1,391,083	$ 1,511,998
Operating expenses:
Purchased transportation and equipment rent, including related party amounts of $1,695, $22 and $65, respectively	824,789	674,143	723,079
Direct personnel and related benefits, including related party amounts of $42,371, $27,532 and $31,932, respectively	456,643	337,618	368,243
Operating supplies and expenses, including related party amounts of $3,887, $826 and $895, respectively	149,394	111,056	120,767
Commission expense	33,894	26,661	31,204
Occupancy expense, including related party amounts of $12,384, $12,925 and $11,794, respectively	37,286	34,586	36,645
General and administrative, including related party amounts of $8,923, $5,688 and $7,633, respectively	39,648	33,267	44,497
Insurance and claims, including related party amounts of $17,997, $16,542 and $17,570, respectively	38,829	19,252	47,418
Depreciation and amortization	67,537	74,141	74,765
Total operating expenses	1,648,020	1,310,724	1,446,618
Income from operations	102,960	80,359	65,380
Interest income	43	47	73
Interest expense	(11,642)	(14,626)	(17,085)
Other non-operating (expense) income	7,220	(1,870)	1,818
Income before income taxes	98,581	63,910	50,186
Income tax expense	24,848	15,778	12,600
Net income	$ 73,733	$ 48,132	$ 37,586
Earnings per common share:
Basic	$ 2.74	$ 1.78	$ 1.34
Diluted	$ 2.74	$ 1.78	$ 1.34
Weighted average number of common shares outstanding:
Basic	26,919	26,997	28,069
Diluted	26,929	27,000	28,070
Dividends declared per common share	$ 0.42	$ 0.21	$ 0.42
Truckload services [Member]
Operating revenues:
Total operating revenues	$ 248,878	$ 201,419	$ 251,574
Brokerage services [Member]
Operating revenues:
Total operating revenues	401,823	336,365	354,940
Intermodal services [Member]
Operating revenues:
Total operating revenues	473,059	393,633	390,299
Dedicated services [Member]
Operating revenues:
Total operating revenues	204,102	127,510	138,664
Value-added services [Member]
Operating revenues:
Total operating revenues	$ 423,118	$ 332,156	$ 376,521