Operating Segments - Reconciliation of Total Reportable Segments' Revenues and EBITDA to Consolidated Revenues and Consolidated Income from Continuing Operations Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Consolidated Revenues	$ 655,774	$ 621,745	$ 1,929,978	$ 1,783,759
Gain from patent litigation	(62,141)	0	(62,141)	0
Amortization of intangibles	(25,533)	(27,162)	(74,990)	(77,944)
Severance, restructuring, and acquisition integration costs	(11,688)	(16,679)	(57,010)	(32,839)
Depreciation expense	(11,700)	(11,700)	(35,600)	(34,600)
Operating income	131,278	61,116	231,987	175,489
Interest expense, net	(14,472)	(19,385)	(46,538)	(66,424)
Non-operating pension benefit (cost)	1,356	(325)	824	(880)
Loss on debt extinguishment	0	(51,594)	(22,990)	(52,441)
Income before taxes	118,162	(10,188)	163,283	55,744
Reportable Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Revenues	659,003	621,745	1,937,867	1,783,759
Deferred revenue adjustments	(3,229)	0	(7,889)	0
Consolidated Revenues	655,774	621,745	1,929,978	1,783,759
Total Segment EBITDA	125,960	117,856	353,344	321,748
Gain from patent litigation	62,141	0	62,141	0
Costs related to patent litigation	(2,634)	0	(2,634)	0
Amortization of intangibles	(25,533)	(27,162)	(74,990)	(77,944)
Severance, restructuring, and acquisition integration costs	(11,688)	(16,679)	(57,010)	(32,839)
Depreciation expense	(11,671)	(11,683)	(35,562)	(34,594)
Purchase accounting effects related to acquisitions	(821)	(2,922)	(2,359)	(4,089)
Amortization of software development intangible assets	(620)	0	(1,344)	0
Loss on sale of assets	0	0	(94)	0
Income from equity method investment	0	2,551	0	5,835
Eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income	$ (627)	$ (845)	$ (1,616)	$ (2,628)