REVENUE Disaggregation of Revenue - Industry (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 2,089,338	$ 1,788,028	$ 3,992,805	$ 3,525,011
SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	604,524	465,704	1,099,231	917,317
Automotive | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	231,886	188,362	439,678	384,803
Technology and healthcare | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	114,388	92,294	217,485	174,952
CPG and retail | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	197,694	126,428	333,052	245,377
Industrial and other | SCS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 60,556	$ 58,620	$ 109,016	$ 112,185