REVENUE Disaggregation of Revenue - Industry (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 2,158,061	$ 1,840,897	$ 6,150,866	$ 5,365,908
SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	628,544	488,506	1,727,775	1,405,823
Automotive | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	250,499	193,284	690,177	578,087
Technology and healthcare | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	123,045	99,078	340,528	274,030
CPG and retail | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	210,965	136,590	544,019	381,967
Industrial and other | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 44,035	$ 59,554	$ 153,051	$ 171,739