Reportable Segments - Reconciliation of Total Reportable Segments' Revenues and EBITDA to Consolidated Revenues and Consolidated Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	$ 475,839	$ 533,098	$ 1,364,176	$ 1,581,590
Amortization of Intangible Assets	(16,104)	(19,026)	(48,306)	(56,258)
Depreciation expense	(10,500)	(10,000)	(31,100)	(30,000)
Severance, restructuring, and acquisition integration costs	(1,357)	(3,047)	(9,448)	(5,566)
Operating income	36,127	57,542	82,965	163,807
Interest expense, net	(15,607)	(14,002)	(43,188)	(41,951)
Total non-operating pension benefit	680	544	2,079	1,684
Consolidated income from continuing operations before taxes	21,200	44,084	41,856	123,540
Reportable Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	475,839	533,098	1,364,176	1,581,590
Total Segment EBITDA	64,641	90,717	173,560	258,331
Amortization of Intangible Assets	(16,104)	(19,026)	(48,306)	(56,258)
Depreciation expense	(10,455)	(9,979)	(31,069)	(29,990)
Severance, restructuring, and acquisition integration costs	(1,357)	(3,047)	(9,448)	(5,566)
Amortization of software development intangible assets	(529)	(85)	(1,245)	(207)
Purchase accounting effects related to acquisitions	0	186	(125)	(532)
Intersegment Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment Elimination	$ (69)	$ (1,224)	$ (402)	$ (1,971)