Goodwill and Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 27, 2021	Jun. 28, 2020	Jun. 27, 2021	Jun. 28, 2020	Dec. 27, 2020
Acquired finite-lived intangible assets:
Gross Value	$ 150.0		$ 150.0		$ 150.0
Accumulated Amortization	(116.5)		(116.5)		(113.9)
Net Value	33.5		33.5		36.1
Total intangible assets: gross value	156.9		156.9		156.9
Total intangible assets: net value	40.4		40.4		43.0
Aggregate amortization expense for finite-lived intangible assets	1.2	$ 1.8	2.6	$ 3.7
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	75.3		75.3		75.3
Accumulated Amortization	(56.7)		(56.7)		(55.7)
Net Value	18.6		18.6		19.6
Contracts and backlog
Acquired finite-lived intangible assets:
Gross Value	33.4		33.4		33.4
Accumulated Amortization	(32.2)		(32.2)		(31.0)
Net Value	1.2		1.2		2.4
Developed technology and technical know-how
Acquired finite-lived intangible assets:
Gross Value	29.9		29.9		29.9
Accumulated Amortization	(25.5)		(25.5)		(25.3)
Net Value	4.4		4.4		4.6
Trade names
Acquired finite-lived intangible assets:
Gross Value	2.0		2.0		2.0
Accumulated Amortization	(2.0)		(2.0)		(1.9)
Net Value	0.0		0.0		0.1
In-process research and development
Acquired finite-lived intangible assets:
Gross Value	9.4		9.4		9.4
Accumulated Amortization	(0.1)		(0.1)		0.0
Net Value	$ 9.3		$ 9.3		$ 9.4