Goodwill and Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Jul. 01, 2018	Jun. 25, 2017	Dec. 31, 2017
Acquired finite-lived intangible assets:
Gross Value	$ 108.9		$ 108.9
Accumulated Amortization	(97.0)		(93.8)
Net Value	11.9		15.1
Total intangible assets: Gross Value	115.8		115.8
Total intangible assets: Net Value	18.8		22.0
Aggregate amortization expense for finite-lived intangible assets	3.2	$ 5.3
Trade names
Acquired finite-lived intangible assets:
Indefinite-lived trade names	6.9		6.9
Customer relationships
Acquired finite-lived intangible assets:
Gross Value	52.6		52.6
Accumulated Amortization	(49.9)		(49.1)
Net Value	2.7		3.5
Contracts and backlog
Acquired finite-lived intangible assets:
Gross Value	29.9		29.9
Accumulated Amortization	(25.7)		(24.8)
Net Value	4.2		5.1
Developed technology and technical know-how
Acquired finite-lived intangible assets:
Gross Value	25.0		25.0
Accumulated Amortization	(20.0)		(18.6)
Net Value	5.0		6.4
Trade names
Acquired finite-lived intangible assets:
Gross Value	1.4		1.4
Accumulated Amortization	(1.4)		(1.3)
Net Value	$ 0.0		$ 0.1