SEGMENT REPORTING - Summary of Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) employee	Dec. 31, 2017 USD ($) employee	Dec. 31, 2016 USD ($) employee
Segment Reporting Information [Line Items]
Revenues	$ 4,137,908	$ 4,291,900	$ 4,276,037	$ 3,925,327	$ 3,959,786	$ 3,784,451	$ 3,710,018	$ 3,415,125	$ 16,631,172	$ 14,869,380	$ 13,144,413
Intersegment revenues									0	0	0
Total Revenues									16,631,172	14,869,380	13,144,413
Net Revenues									2,705,235	2,368,050	2,277,528
Income (loss) from operations	255,517	$ 245,973	$ 219,008	$ 191,585	210,876	$ 194,465	$ 181,820	$ 187,958	912,083	775,119	837,531
Depreciation and amortization									96,729	92,977	74,669
Total assets	4,427,412				4,235,834				$ 4,427,412	$ 4,235,834	$ 3,687,758
Average headcount (employee) | employee									15,204	14,687	13,670
Operating Segments | NAST
Segment Reporting Information [Line Items]
Revenues									$ 11,247,900	$ 9,728,810	$ 8,737,716
Intersegment revenues									545,177	462,390	298,438
Total Revenues									11,793,077	10,191,200	9,036,154
Net Revenues									1,788,498	1,525,064	1,524,355
Income (loss) from operations									773,846	628,110	674,436
Depreciation and amortization									24,510	23,230	22,126
Total assets	2,345,455				2,277,252				$ 2,345,455	$ 2,277,252	$ 2,088,611
Average headcount (employee) | employee									6,938	6,907	6,773
Operating Segments | Global Forwarding
Segment Reporting Information [Line Items]
Revenues									$ 2,487,744	$ 2,140,987	$ 1,574,686
Intersegment revenues									48,343	30,198	30,311
Total Revenues									2,536,087	2,171,185	1,604,997
Net Revenues									543,906	485,280	397,537
Income (loss) from operations									91,626	91,842	80,931
Depreciation and amortization									35,148	33,308	23,099
Total assets	969,736				821,182				$ 969,736	$ 821,182	$ 703,741
Average headcount (employee) | employee									4,711	4,310	3,673
Operating Segments | Robinson Fresh
Segment Reporting Information [Line Items]
Revenues									$ 2,268,900	$ 2,415,740	$ 2,344,131
Intersegment revenues									211,286	167,292	119,403
Total Revenues									2,480,186	2,583,032	2,463,534
Net Revenues									234,046	226,059	234,794
Income (loss) from operations									59,735	53,374	75,757
Depreciation and amortization									4,506	4,730	3,782
Total assets	401,561				434,080				$ 401,561	$ 434,080	$ 376,654
Average headcount (employee) | employee									903	957	942
Operating Segments | All Other and Corporate
Segment Reporting Information [Line Items]
Revenues									$ 626,628	$ 583,843	$ 487,880
Intersegment revenues									20,951	18,174	2,211
Total Revenues									647,579	602,017	490,091
Net Revenues									138,785	131,647	120,842
Income (loss) from operations									(13,124)	1,793	6,407
Depreciation and amortization									32,565	31,709	25,662
Total assets	710,660				703,320				$ 710,660	$ 703,320	$ 518,752
Average headcount (employee) | employee									2,652	2,513	2,282
Eliminations
Segment Reporting Information [Line Items]
Revenues									$ 0	$ 0	$ 0
Intersegment revenues									(825,757)	(678,054)	(450,363)
Total Revenues									(825,757)	(678,054)	(450,363)
Net Revenues									0	0	0
Income (loss) from operations									0	0	0
Depreciation and amortization									0	0	0
Total assets	$ 0				$ 0				$ 0	$ 0	$ 0
Average headcount (employee) | employee									0	0	0