Reportable Segments - Operating Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Segment revenues	$ 620,318	$ 655,774	$ 1,845,023	$ 1,929,978
Depreciation expense	12,100	11,700	37,200	35,600
Amortization of intangibles	22,243	25,533	67,952	74,990
Severance, restructuring, and acquisition integration costs	(4,045)	(11,688)	(10,904)	(57,010)
Goodwill and other asset impairment	342,146	0	342,146	0
Segment assets	3,441,995		3,441,995		$ 3,779,321
Enterprise Solutions
Segment Reporting Information [Line Items]
Segment revenues	368,080	388,851	1,064,469	1,134,876
Severance, restructuring, and acquisition integration costs	(4,045)	(9,528)	(10,904)	(46,949)
Industrial Solutions
Segment Reporting Information [Line Items]
Segment revenues	252,238	266,923	780,554	795,102
Severance, restructuring, and acquisition integration costs	0	(2,160)	0	(10,061)
Reportable Segment
Segment Reporting Information [Line Items]
Segment revenues	620,318	659,003	1,845,023	1,937,867
Segment EBITDA	101,428	125,960	289,386	353,344
Depreciation expense	12,147	11,671	37,170	35,562
Amortization of intangibles	22,243	25,533	67,952	74,990
Amortization of software development intangible assets	1,197	620	3,206	1,344
Severance, restructuring, and acquisition integration costs	(4,045)	(11,688)	(10,904)	(57,010)
Purchase accounting effects of acquisitions	(186)	821	1,845	2,359
Goodwill and other asset impairment	342,146	0	342,146	0
Deferred revenue adjustments	0	3,229	0	7,889
Segment assets	1,292,010	1,215,131	1,292,010	1,215,131
Reportable Segment | Enterprise Solutions
Segment Reporting Information [Line Items]
Segment revenues	368,080	392,080	1,064,469	1,142,765
Segment EBITDA	56,814	72,210	149,855	199,943
Depreciation expense	7,381	7,092	22,655	21,465
Amortization of intangibles	9,780	12,322	29,270	35,301
Amortization of software development intangible assets	1,161	620	3,119	1,344
Severance, restructuring, and acquisition integration costs	(4,045)	(9,528)	(10,904)	(46,949)
Purchase accounting effects of acquisitions	(186)	821	1,845	2,359
Goodwill and other asset impairment	342,146		342,146
Deferred revenue adjustments		3,229		7,889
Segment assets	836,540	766,505	836,540	766,505
Reportable Segment | Industrial Solutions
Segment Reporting Information [Line Items]
Segment revenues	252,238	266,923	780,554	795,102
Segment EBITDA	44,614	53,750	139,531	153,401
Depreciation expense	4,766	4,579	14,515	14,097
Amortization of intangibles	12,463	13,211	38,682	39,689
Amortization of software development intangible assets	36	0	87	0
Severance, restructuring, and acquisition integration costs	0	(2,160)	0	(10,061)
Purchase accounting effects of acquisitions	0	0	0	0
Goodwill and other asset impairment	0		0
Deferred revenue adjustments		0		0
Segment assets	455,470	448,626	455,470	448,626
Affiliate revenues | Reportable Segment
Segment Reporting Information [Line Items]
Segment revenues	929	1,791	3,203	4,379
Affiliate revenues | Reportable Segment | Enterprise Solutions
Segment Reporting Information [Line Items]
Segment revenues	927	1,776	3,190	4,318
Affiliate revenues | Reportable Segment | Industrial Solutions
Segment Reporting Information [Line Items]
Segment revenues	$ 2	$ 15	$ 13	$ 61