SEGMENT REPORTING - Summary of Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) employee	Jun. 30, 2017 USD ($) employee	Jun. 30, 2018 USD ($) employee	Jun. 30, 2017 USD ($) employee	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Total revenues	$ 4,276,037	$ 3,710,018	$ 8,201,364	$ 7,125,143
Net revenues	671,483	573,789	1,297,408	1,142,355
Income from operations	219,008	181,820	410,593	369,778
Depreciation and amortization	24,238	22,946	48,479	45,377
Total assets	$ 4,453,284	$ 3,965,889	$ 4,453,284	$ 3,965,889	$ 4,235,834
Average headcount (employee) | employee	15,229	14,620	15,177	14,454
NAST
Segment Reporting Information [Line Items]
Total revenues	$ 3,014,221	$ 2,493,794	$ 5,800,777	$ 4,854,200
Net revenues	436,813	359,906	851,582	732,346
Income from operations	184,566	140,284	358,644	296,161
Depreciation and amortization	6,085	5,706	12,218	11,296
Total assets	$ 2,470,743	$ 2,189,711	$ 2,470,743	$ 2,189,711
Average headcount (employee) | employee	6,957	7,003	6,921	6,926
Global Forwarding
Segment Reporting Information [Line Items]
Total revenues	$ 632,472	$ 536,260	$ 1,195,590	$ 1,013,191
Net revenues	144,031	121,023	267,068	227,569
Income from operations	29,788	27,675	38,009	43,881
Depreciation and amortization	8,753	8,099	17,662	16,119
Total assets	$ 861,080	$ 741,443	$ 861,080	$ 741,443
Average headcount (employee) | employee	4,736	4,021	4,743	3,977
Robinson Fresh
Segment Reporting Information [Line Items]
Total revenues	$ 671,155	$ 696,672	$ 1,269,970	$ 1,280,457
Net revenues	55,537	60,846	109,407	117,683
Income from operations	9,232	14,249	18,539	28,901
Depreciation and amortization	1,144	1,198	2,317	2,344
Total assets	$ 445,926	$ 455,214	$ 445,926	$ 455,214
Average headcount (employee) | employee	909	980	913	971
All Other and Corporate
Segment Reporting Information [Line Items]
Total revenues	$ 162,403	$ 146,314	$ 326,795	$ 289,832
Net revenues	35,102	32,014	69,351	64,757
Income from operations	(4,578)	(388)	(4,599)	835
Depreciation and amortization	8,256	7,943	16,282	15,618
Total assets	$ 675,535	$ 579,521	$ 675,535	$ 579,521
Average headcount (employee) | employee	2,627	2,616	2,600	2,580
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	$ 4,276,037	$ 3,710,018	$ 8,201,364	$ 7,125,143
Operating Segments | NAST
Segment Reporting Information [Line Items]
Total revenues	2,878,904	2,381,551	5,541,915	4,640,803
Operating Segments | Global Forwarding
Segment Reporting Information [Line Items]
Total revenues	617,597	528,820	1,171,351	997,608
Operating Segments | Robinson Fresh
Segment Reporting Information [Line Items]
Total revenues	621,024	657,003	1,171,493	1,207,448
Operating Segments | All Other and Corporate
Segment Reporting Information [Line Items]
Total revenues	158,512	142,644	316,605	279,284
Intersegment revenues
Segment Reporting Information [Line Items]
Total revenues	(204,214)	(163,022)	(391,768)	(312,537)
Intersegment revenues | NAST
Segment Reporting Information [Line Items]
Total revenues	135,317	112,243	258,862	213,397
Intersegment revenues | Global Forwarding
Segment Reporting Information [Line Items]
Total revenues	14,875	7,440	24,239	15,583
Intersegment revenues | Robinson Fresh
Segment Reporting Information [Line Items]
Total revenues	50,131	39,669	98,477	73,009
Intersegment revenues | All Other and Corporate
Segment Reporting Information [Line Items]
Total revenues	$ 3,891	$ 3,670	$ 10,190	$ 10,548