REVENUE Disaggregation of Revenue - Geographical (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 2,382,237	$ 1,895,282	$ 4,603,859	$ 4,056,588
United States
Disaggregation of Revenue [Line Items]
Revenues	2,131,624	1,703,799	4,114,686	3,621,438
Canada
Disaggregation of Revenue [Line Items]
Revenues	127,291	97,536	249,449	216,882
Europe
Disaggregation of Revenue [Line Items]
Revenues	68,142	56,249	135,230	128,200
Mexico
Disaggregation of Revenue [Line Items]
Revenues	55,180	37,698	104,494	90,068
SCS
Disaggregation of Revenue [Line Items]
Revenues	775,630	519,318	1,482,330	1,147,765
Operating Segments | FMS
Disaggregation of Revenue [Line Items]
Revenues	1,408,241	1,198,177	2,743,726	2,538,414
Operating Segments | FMS | United States
Disaggregation of Revenue [Line Items]
Revenues	1,263,250	1,081,448	2,461,234	2,278,969
Operating Segments | FMS | Canada
Disaggregation of Revenue [Line Items]
Revenues	76,849	60,480	147,262	131,245
Operating Segments | FMS | Europe
Disaggregation of Revenue [Line Items]
Revenues	68,142	56,249	135,230	128,200
Operating Segments | FMS | Mexico
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | SCS
Disaggregation of Revenue [Line Items]
Revenues	775,630	519,318	1,482,330	1,147,765
Operating Segments | SCS | United States
Disaggregation of Revenue [Line Items]
Revenues	661,715	441,332	1,263,013	963,857
Operating Segments | SCS | Canada
Disaggregation of Revenue [Line Items]
Revenues	58,735	40,288	114,823	93,840
Operating Segments | SCS | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | SCS | Mexico
Disaggregation of Revenue [Line Items]
Revenues	55,180	37,698	104,494	90,068
Operating Segments | DTS
Disaggregation of Revenue [Line Items]
Revenues	354,711	293,944	675,218	628,832
Operating Segments | DTS | United States
Disaggregation of Revenue [Line Items]
Revenues	354,711	293,944	675,218	628,832
Operating Segments | DTS | Canada
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | DTS | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments | DTS | Mexico
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(156,345)	(116,157)	(297,415)	(258,423)
Eliminations | United States
Disaggregation of Revenue [Line Items]
Revenues	(148,052)	(112,925)	(284,779)	(250,220)
Eliminations | Canada
Disaggregation of Revenue [Line Items]
Revenues	(8,293)	(3,232)	(12,636)	(8,203)
Eliminations | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Eliminations | Mexico
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0