Goodwill and Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019	Dec. 29, 2019
Acquired finite-lived intangible assets:
Gross Value	$ 147.5		$ 147.5		$ 139.7
Accumulated Amortization	(112.4)		(112.4)		(107.1)
Net Value	35.1		35.1		32.6
Total intangible assets: gross value	154.4		154.4		146.6
Total intangible assets: net value	42.0		42.0		39.5
Aggregate amortization expense for finite-lived intangible assets	1.7	$ 1.7	5.4	$ 5.2
Trade names
Acquired finite-lived intangible assets:
Indefinite-lived trade names	6.9		6.9		6.9
Customer relationships
Acquired finite-lived intangible assets:
Gross Value	75.0		75.0		72.3
Accumulated Amortization	(55.2)		(55.2)		(53.3)
Net Value	19.8		19.8		19.0
Contracts and backlog
Acquired finite-lived intangible assets:
Gross Value	32.7		32.7		32.0
Accumulated Amortization	(30.3)		(30.3)		(28.4)
Net Value	2.4		2.4		3.6
Developed technology and technical know-how
Acquired finite-lived intangible assets:
Gross Value	28.6		28.6		25.0
Accumulated Amortization	(25.1)		(25.1)		(23.8)
Net Value	3.5		3.5		1.2
Trade names
Acquired finite-lived intangible assets:
Gross Value	2.0		2.0		1.9
Accumulated Amortization	(1.8)		(1.8)		(1.6)
Net Value	0.2		0.2		0.3
In-process research and development
Acquired finite-lived intangible assets:
Gross Value	9.2		9.2		8.5
Accumulated Amortization	0.0		0.0		0.0
Net Value	$ 9.2		$ 9.2		$ 8.5