Revenues - Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 655,774	$ 621,745	$ 1,929,978	$ 1,783,759
Enterprise Solutions
Disaggregation of Revenue [Line Items]
Revenues	388,851	360,842	1,134,876	1,023,924
Industrial Solutions
Disaggregation of Revenue [Line Items]
Revenues	266,923	260,903	795,102	759,835
Products
Disaggregation of Revenue [Line Items]
Revenues	611,967	577,594	1,804,202	1,651,976
Products | Enterprise Solutions
Disaggregation of Revenue [Line Items]
Revenues	368,389	342,216	1,080,549	968,855
Products | Industrial Solutions
Disaggregation of Revenue [Line Items]
Revenues	243,578	235,378	723,653	683,121
Support & Services
Disaggregation of Revenue [Line Items]
Revenues	43,807	44,151	125,776	131,783
Support & Services | Enterprise Solutions
Disaggregation of Revenue [Line Items]
Revenues	20,462	18,626	54,327	55,069
Support & Services | Industrial Solutions
Disaggregation of Revenue [Line Items]
Revenues	$ 23,345	$ 25,525	$ 71,449	$ 76,714