REVENUE - Disaggregation of Revenue by Geographical Market and Industry (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 8,420,091	$ 8,925,801	$ 8,413,946
United States
Disaggregation of Revenue [Line Items]
Revenues	7,515,716	7,900,014	7,408,529
Canada
Disaggregation of Revenue [Line Items]
Revenues	459,823	497,150	466,321
Europe
Disaggregation of Revenue [Line Items]
Revenues	254,979	302,986	317,093
Mexico
Disaggregation of Revenue [Line Items]
Revenues	189,573	222,358	198,147
Singapore
Disaggregation of Revenue [Line Items]
Revenues		3,293	23,856
SCS
Disaggregation of Revenue [Line Items]
Revenues	2,544,420	2,551,271	2,398,144
Operating Segments | FMS
Disaggregation of Revenue [Line Items]
Revenues	5,170,467	5,571,403	5,258,693
Operating Segments | FMS | United States
Disaggregation of Revenue [Line Items]
Revenues	4,646,290	4,965,461	4,639,494
Operating Segments | FMS | Canada
Disaggregation of Revenue [Line Items]
Revenues	269,198	302,956	302,106
Operating Segments | FMS | Europe
Disaggregation of Revenue [Line Items]
Revenues	254,979	302,986	317,093
Operating Segments | FMS | Mexico
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | FMS | Singapore
Disaggregation of Revenue [Line Items]
Revenues		0	0
Operating Segments | SCS
Disaggregation of Revenue [Line Items]
Revenues	2,544,420	2,551,271	2,398,144
Operating Segments | SCS | United States
Disaggregation of Revenue [Line Items]
Revenues	2,146,936	2,110,240	1,990,486
Operating Segments | SCS | Canada
Disaggregation of Revenue [Line Items]
Revenues	207,911	215,380	185,655
Operating Segments | SCS | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | SCS | Mexico
Disaggregation of Revenue [Line Items]
Revenues	189,573	222,358	198,147
Operating Segments | SCS | Singapore
Disaggregation of Revenue [Line Items]
Revenues		3,293	23,856
Operating Segments | DTS
Disaggregation of Revenue [Line Items]
Revenues	1,229,374	1,417,483	1,333,313
Operating Segments | DTS | United States
Disaggregation of Revenue [Line Items]
Revenues	1,229,374	1,417,483	1,333,313
Operating Segments | DTS | Canada
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | DTS | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | DTS | Mexico
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | DTS | Singapore
Disaggregation of Revenue [Line Items]
Revenues		0	0
Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(524,170)	(614,356)	(576,204)
Eliminations | United States
Disaggregation of Revenue [Line Items]
Revenues	(506,884)	(593,170)	(554,764)
Eliminations | Canada
Disaggregation of Revenue [Line Items]
Revenues	(17,286)	(21,186)	(21,440)
Eliminations | Europe
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Eliminations | Mexico
Disaggregation of Revenue [Line Items]
Revenues	$ 0	0	0
Eliminations | Singapore
Disaggregation of Revenue [Line Items]
Revenues		$ 0	$ 0