Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Total revenue	$ 1,204,535	$ 1,271,132
Operating expenses:
Salaries, wages, and benefits	363,855	361,673
Fuel	138,439	144,816
Operations and maintenance	79,760	85,020
Insurance and claims	50,136	59,148
Operating taxes and licenses	21,803	23,150
Communications	5,083	5,292
Depreciation and amortization of property and equipment	100,937	93,863
Amortization of intangibles	10,693	10,509
Rental expense	35,545	52,875
Purchased transportation	269,349	324,283
Miscellaneous operating expenses	12,636	16,759
Total operating expenses	1,088,236	1,177,388
Operating income	116,299	93,744
Other (expenses) income:
Interest income	1,016	572
Interest expense	(7,348)	(6,764)
Other income, net	6,139	2,155
Other (expenses) income, net	(193)	(4,037)
Income before income taxes	116,106	89,707
Income tax expense	27,923	18,975
Net income	88,183	70,732
Net income attributable to noncontrolling interest	(245)	(368)
Net income attributable to Knight-Swift	$ 87,938	$ 70,364
Earnings per share:
Basic (in dollars per share)	$ 0.51	$ 0.39
Diluted (in dollars per share)	0.51	0.39
Dividends declared per share: (in dollars per share)	$ 0.06	$ 0.06
Weighted average shares outstanding:
Basic (in shares)	172,971	178,160
Diluted (in shares)	173,608	179,241
Revenue, excluding fuel surcharge [Member]
Total revenue	$ 1,078,138	$ 1,124,172
Fuel surcharge revenue [Member]
Total revenue	$ 126,397	$ 146,960