Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Sep. 27, 2020	Jun. 30, 2020	Dec. 29, 2019	Feb. 27, 2019
Business Acquisition [Line Items]
Goodwill	$ 475.3		$ 455.6
FTT
Business Acquisition [Line Items]
Accounts receivable				$ 8.1
Unbilled receivables				4.9
Inventoried costs				7.8
Other current assets				1.8
Property and equipment				5.7
Intangible assets				30.8
Goodwill				23.3
Total identifiable net assets acquired				82.4
Total identifiable net liabilities assumed				(7.5)
Net assets before noncontrolling interest				74.9
Noncontrolling interest				(14.9)
Net assets acquired, excluding cash				$ 60.0
CPI ASC Signal Division, Inc.
Business Acquisition [Line Items]
Accounts receivable		$ 5.6
Unbilled receivables		0.9
Inventoried costs		10.4
Other current assets		3.2
Property and equipment		10.0
Intangible assets		4.3
Goodwill		9.7
Total identifiable net assets acquired		44.1
Total identifiable net liabilities assumed		(11.2)
Net assets before noncontrolling interest		$ 32.9