Consolidated Statements of Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues
Revenue	$ 422,477	$ 413,862	$ 855,045	$ 829,225
Operating expenses
Salaries, wages, and benefits	139,987	130,521	275,381	255,084
Fuel and fuel taxes	29,874	47,374	70,197	94,278
Vehicle rents	21,335	18,579	43,212	37,555
Depreciation and amortization, net of (gain) loss on sale of property	26,283	24,752	52,086	47,814
Operating expenses and supplies	28,126	29,968	57,800	57,913
Insurance premiums and claims	21,283	19,266	47,306	43,619
Operating taxes and licenses	3,720	3,406	7,397	6,579
Communications and utilities	2,256	2,185	4,708	4,450
General and other operating expenses	15,970	17,115	37,229	34,594
Gain on sale of subsidiary		(670)		(670)
Total operating expenses	406,200	405,075	842,436	807,800
Operating income	16,277	8,787	12,609	21,425
Other expense (income)
Interest expense, net	4,862	5,296	10,283	10,899
Loss on sale of equity method investment			2,000
Equity in loss of affiliated companies		90		179
Other, net				26
Nonoperating Income (Expense), Total	(4,862)	(5,386)	(12,283)	(11,104)
Income before income tax provision	11,415	3,401	326	10,321
Income tax provision	2,387	415	530	2,316
Net total and comprehensive income (loss)	9,028	2,986	(204)	8,005
Net total and comprehensive income (loss) attributable to noncontrolling interest	(470)	314	(486)	612
Net total and comprehensive income attributable to controlling interest	$ 9,498	$ 2,672	$ 282	$ 7,393
Earnings (loss) per share
Basic earnings per share (in dollars per share)	$ 0.19	$ 0.05	$ 0.01	$ 0.15
Basic weighted average shares outstanding (in shares)	49,499	48,742	49,358	48,569
Diluted earnings (loss) per share (in dollars per share)	$ 0.18	$ 0.05	$ 0.00	$ 0.15
Diluted weighted average shares outstanding (in shares)	50,215	49,312	49,518	49,184
Cargo and Freight [Member]
Revenues
Revenue	$ 393,964	$ 371,184	$ 786,784	$ 746,496
Fuel Surcharge [Member]
Revenues
Revenue	28,513	42,678	68,261	82,729
Shipping and Handling [Member]
Operating expenses
Purchased transportation	$ 117,366	$ 112,579	$ 247,120	$ 226,584