Schedule of Income from Discontinued Operations (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Other income (expense)
Income from discontinued operations	$ 4,897	$ 9,995
Mode [Member] | Discontinued Operations Disposed of By Sale [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Revenue	284,360	542,988
Transportation costs	249,161	476,037
Gross margin	35,199	66,951
Costs and expenses:
Salaries and benefits	4,022	7,726
General and administrative	24,392	45,600
Depreciation and amortization	237	479
Total costs and expenses	28,651	53,805
Operating income from discontinued operations	6,548	13,146
Other income (expense)
Interest income	8	18
Other, net	(8)	(13)
Total other income		5
Income from discontinued operations before income taxes	6,548	13,151
Provision for income taxes	1,651	3,156
Income from discontinued operations	$ 4,897	$ 9,995