SEGMENT REPORTING - Reportable Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) employee	Mar. 31, 2019 USD ($) employee	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Total revenues	$ 3,805,008	$ 3,751,210
Net revenues	567,953	678,800
Income (loss) from operations	109,440	224,550
Depreciation and amortization	24,393	24,560
Total assets	$ 4,848,320	$ 4,697,444	$ 4,641,060
Average headcount (employee) | employee	15,450	15,381
Operating Segments | NAST
Segment Reporting Information [Line Items]
Total revenues	$ 2,823,745	$ 2,796,784
Net revenues	372,778	486,550
Income (loss) from operations	98,526	211,283
Depreciation and amortization	5,254	6,259
Total assets	$ 2,942,719	$ 2,693,668
Average headcount (employee) | employee	7,038	7,424
Operating Segments | Global Forwarding
Segment Reporting Information [Line Items]
Total revenues	$ 530,384	$ 537,567
Net revenues	128,314	127,236
Income (loss) from operations	11,959	14,203
Depreciation and amortization	9,149	8,926
Total assets	$ 934,625	$ 1,001,881
Average headcount (employee) | employee	4,824	4,707
Operating Segments | All Other and Corporate
Segment Reporting Information [Line Items]
Total revenues	$ 450,879	$ 416,859
Net revenues	66,861	65,014
Income (loss) from operations	(1,045)	(936)
Depreciation and amortization	9,990	9,375
Total assets	$ 970,976	$ 1,001,895
Average headcount (employee) | employee	3,588	3,250