Reportable Segments - Operating Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Segment revenues	$ 637,530	$ 668,639	$ 1,224,705	$ 1,274,204
Depreciation expense	12,300	12,000	25,000	23,900
Amortization of intangibles	22,368	25,039	45,709	49,457
Severance, restructuring, and acquisition integration costs	(3,082)	(24,928)	(6,860)	(45,322)
Segment assets	3,822,980		3,822,980		$ 3,779,321
Enterprise Solutions
Segment Reporting Information [Line Items]
Segment revenues	369,862	396,893	696,389	746,025
Severance, restructuring, and acquisition integration costs	(3,082)	(22,887)	(6,860)	(37,421)
Industrial Solutions
Segment Reporting Information [Line Items]
Segment revenues	267,668	271,746	528,316	528,179
Severance, restructuring, and acquisition integration costs	0	(2,041)	0	(7,901)
Reportable Segment
Segment Reporting Information [Line Items]
Segment revenues	637,530	671,441	1,224,705	1,278,864
Segment EBITDA	100,941	123,506	187,958	227,384
Depreciation expense	12,301	12,026	25,021	23,891
Amortization of intangibles	22,368	25,039	45,709	49,457
Amortization of software development intangible assets	1,072	488	2,009	724
Severance, restructuring, and acquisition integration costs	(3,082)	(24,928)	(6,860)	(45,322)
Purchase accounting effects of acquisitions	718	1,036	2,031	1,538
Deferred revenue adjustments	0	2,802	0	4,660
Segment assets	1,301,296	1,196,219	1,301,296	1,196,219
Reportable Segment | Enterprise Solutions
Segment Reporting Information [Line Items]
Segment revenues	369,862	399,695	696,389	750,685
Segment EBITDA	53,483	70,281	93,041	127,733
Depreciation expense	7,540	7,153	15,273	14,373
Amortization of intangibles	9,320	11,809	19,490	22,979
Amortization of software development intangible assets	1,044	488	1,958	724
Severance, restructuring, and acquisition integration costs	(3,082)	(22,887)	(6,860)	(37,421)
Purchase accounting effects of acquisitions	718	1,036	2,031	1,538
Deferred revenue adjustments		2,802		4,660
Segment assets	822,402	759,334	822,402	759,334
Reportable Segment | Industrial Solutions
Segment Reporting Information [Line Items]
Segment revenues	267,668	271,746	528,316	528,179
Segment EBITDA	47,458	53,225	94,917	99,651
Depreciation expense	4,761	4,873	9,748	9,518
Amortization of intangibles	13,048	13,230	26,219	26,478
Amortization of software development intangible assets	28	0	51	0
Severance, restructuring, and acquisition integration costs	0	(2,041)	0	(7,901)
Purchase accounting effects of acquisitions	0	0	0	0
Deferred revenue adjustments		0		0
Segment assets	478,894	436,885	478,894	436,885
Affiliate revenues | Reportable Segment
Segment Reporting Information [Line Items]
Segment revenues	893	1,513	2,280	2,588
Affiliate revenues | Reportable Segment | Enterprise Solutions
Segment Reporting Information [Line Items]
Segment revenues	893	1,496	2,263	2,542
Affiliate revenues | Reportable Segment | Industrial Solutions
Segment Reporting Information [Line Items]
Segment revenues	$ 0	$ 17	$ 17	$ 46