REVENUE Disaggregation of Revenue - Geographical (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,244,993	$ 2,089,904	$ 4,425,320	$ 3,994,109
United States
Disaggregation of Revenue [Line Items]
Total revenue	1,988,488	1,835,136	3,915,282	3,493,719
Canada
Disaggregation of Revenue [Line Items]
Total revenue	124,473	117,839	242,794	230,934
Europe
Disaggregation of Revenue [Line Items]
Total revenue	75,889	80,493	154,531	163,289
Mexico
Disaggregation of Revenue [Line Items]
Total revenue	56,143	50,070	109,420	94,102
Singapore
Disaggregation of Revenue [Line Items]
Total revenue	0	6,366	3,293	12,065
FMS
Disaggregation of Revenue [Line Items]
Total revenue	1,233,438	1,154,758	2,428,473	2,265,286
DTS
Disaggregation of Revenue [Line Items]
Total revenue	362,244	330,622	711,865	629,592
SCS
Disaggregation of Revenue [Line Items]
Total revenue	649,311	604,524	1,284,982	1,099,231
Operating Segments | FMS
Disaggregation of Revenue [Line Items]
Total revenue	1,390,910	1,295,729	2,742,509	2,538,779
Operating Segments | FMS | United States
Disaggregation of Revenue [Line Items]
Total revenue	1,238,631	1,139,742	2,437,574	2,225,189
Operating Segments | FMS | Canada
Disaggregation of Revenue [Line Items]
Total revenue	76,390	75,494	150,404	150,301
Operating Segments | FMS | Europe
Disaggregation of Revenue [Line Items]
Total revenue	75,889	80,493	154,531	163,289
Operating Segments | FMS | Mexico
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | FMS | Singapore
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | DTS
Disaggregation of Revenue [Line Items]
Total revenue	362,244	330,622	711,865	629,592
Operating Segments | DTS | United States
Disaggregation of Revenue [Line Items]
Total revenue	362,244	330,622	711,865	629,592
Operating Segments | DTS | Canada
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | DTS | Europe
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | DTS | Mexico
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | DTS | Singapore
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | SCS
Disaggregation of Revenue [Line Items]
Total revenue	649,311	604,524	1,284,982	1,099,231
Operating Segments | SCS | United States
Disaggregation of Revenue [Line Items]
Total revenue	539,623	500,341	1,069,016	902,223
Operating Segments | SCS | Canada
Disaggregation of Revenue [Line Items]
Total revenue	53,545	47,747	103,253	90,841
Operating Segments | SCS | Europe
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | SCS | Mexico
Disaggregation of Revenue [Line Items]
Total revenue	56,143	50,070	109,420	94,102
Operating Segments | SCS | Singapore
Disaggregation of Revenue [Line Items]
Total revenue	0	6,366	3,293	12,065
Eliminations
Disaggregation of Revenue [Line Items]
Total revenue	(157,472)	(140,971)	(314,036)	(273,493)
Eliminations | United States
Disaggregation of Revenue [Line Items]
Total revenue	(152,010)	(135,569)	(303,173)	(263,285)
Eliminations | Canada
Disaggregation of Revenue [Line Items]
Total revenue	(5,462)	(5,402)	(10,863)	(10,208)
Eliminations | Europe
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Eliminations | Mexico
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Eliminations | Singapore
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Eliminations | FMS
Disaggregation of Revenue [Line Items]
Total revenue	157,472	140,971	314,036	273,493
Eliminations | DTS
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Eliminations | SCS
Disaggregation of Revenue [Line Items]
Total revenue	$ 0	$ 0	$ 0	$ 0