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		6 Months Ended
	Jul. 04, 2021	Jun. 28, 2020	Jul. 04, 2021	Jun. 28, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	$ 601,974	$ 424,811	$ 1,138,355	$ 888,337
Amortization of Intangible Assets	(9,102)	(16,017)	(19,049)	(32,202)
Depreciation expense	(11,400)	(10,300)	(22,900)	(20,600)
Severance, restructuring, and acquisition integration costs	(3,040)	(4,472)	(8,211)	(8,091)
Operating income	65,957	17,130	117,405	46,838
Interest Income (Expense), Net	14,878	14,257	30,389	27,581
Non-operating pension benefit	1,445	700	2,129	1,399
Consolidated income from continuing operations before taxes	52,524	3,573	89,145	20,656
OTN Systems N.V.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Amortization of Intangible Assets	(700)		(2,300)
Inventory adjustment	1,200		2,000
Reportable Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	602,823	424,811	1,139,204	888,337
Adjustments related to acquisitions	849	0	849	0
Total Segment EBITDA	92,000	48,680	171,469	108,919
Amortization of Intangible Assets	(9,102)	(16,017)	(19,049)	(32,202)
Depreciation expense	(11,367)	(10,332)	(22,927)	(20,614)
Severance, restructuring, and acquisition integration costs	(3,040)	(4,472)	(8,211)	(8,091)
Amortization of software development intangible assets	(607)	(386)	(1,296)	(716)
Purchase accounting effects related to acquisitions	(1,912)	(105)	(2,533)	(125)
Impairment of assets held-for-use			3,600
Impairment of assets to be held for sale			3,400
Collection of receivables, previously written off	100		1,500
Reportable Segment | Opterna International Corp.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Business combination, increase (decrease) in earn-out liability			(5,800)
Reportable Segment | OTN Systems N.V.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Inventory adjustment	1,200		2,000
Deferred revenue adjustment	800		800
Intersegment Eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment Elimination	$ (15)	$ (238)	$ (48)	$ (333)