SEGMENT REPORTING - Summary of Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) employee	Dec. 31, 2018 USD ($) employee	Dec. 31, 2017 USD ($) employee
Segment Reporting Information [Line Items]
Total revenues	$ 3,793,326	$ 3,856,132	$ 3,908,840	$ 3,751,210	$ 4,137,908	$ 4,291,900	$ 4,276,037	$ 3,925,327	$ 15,309,508	$ 16,631,172	$ 14,869,380
Net Revenues									2,586,310	2,705,235	2,368,050
Income (loss) from operations	136,806	$ 201,085	$ 227,535	$ 224,550	255,517	$ 245,973	$ 219,008	$ 191,585	789,976	912,083	775,119
Depreciation and amortization									100,449	96,729	92,977
Total assets	4,641,060				4,427,412				$ 4,641,060	$ 4,427,412	$ 4,235,834
Average headcount (employee) | employee									15,551	15,204	14,687
Operating Segments | NAST
Segment Reporting Information [Line Items]
Total revenues									$ 11,283,692	$ 12,346,757	$ 10,728,835
Net Revenues									1,797,369	1,906,261	1,626,174
Income (loss) from operations									722,763	821,844	661,108
Depreciation and amortization									24,508	25,290	23,866
Total assets	2,550,010				2,567,120				$ 2,550,010	$ 2,567,120	$ 2,506,137
Average headcount (employee) | employee									7,354	7,387	7,316
Operating Segments | Global Forwarding
Segment Reporting Information [Line Items]
Total revenues									$ 2,327,913	$ 2,487,744	$ 2,140,987
Net Revenues									533,976	543,906	485,280
Income (loss) from operations									80,527	91,626	91,842
Depreciation and amortization									36,720	35,148	33,308
Total assets	1,021,592				969,736				$ 1,021,592	$ 969,736	$ 821,182
Average headcount (employee) | employee									4,766	4,711	4,310
Operating Segments | All Other and Corporate
Segment Reporting Information [Line Items]
Total revenues									$ 1,697,903	$ 1,796,671	$ 1,999,558
Net Revenues									254,965	255,068	256,596
Income (loss) from operations									(13,314)	(1,387)	22,169
Depreciation and amortization									39,221	36,291	35,803
Total assets	$ 1,069,458				$ 890,556				$ 1,069,458	$ 890,556	$ 908,515
Average headcount (employee) | employee									3,431	3,106	3,061