GOODWILL AND OTHER INTANGIBLE ASSETS - Estimated Amortization Expense on Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Goodwill [Line Items]
Amortization expense	$ 9,157	$ 6,094	$ 26,875	$ 18,282
Estimated amortization expense
Remainder of 2017	9,390		9,390
2018	37,037		37,037
2019	37,037		37,037
2020	26,773		26,773
2021	13,252		13,252
Thereafter	26,631		26,631
Net	150,120		150,120		$ 157,050
NAST
Estimated amortization expense
Remainder of 2017	1,955		1,955
2018	7,820		7,820
2019	7,820		7,820
2020	260		260
2021	260		260
Thereafter	706		706
Global Forwarding
Estimated amortization expense
Remainder of 2017	7,267		7,267
2018	29,217		29,217
2019	29,217		29,217
2020	26,513		26,513
2021	12,992		12,992
Thereafter	25,925		25,925
Robinson Fresh
Estimated amortization expense
Remainder of 2017	0		0
2018	0		0
2019	0		0
2020	0		0
2021	0		0
Thereafter	0		0
All Other and Corporate
Estimated amortization expense
Remainder of 2017	168		168
2018	0		0
2019	0		0
2020	0		0
2021	0		0
Thereafter	$ 0		$ 0