Goodwill and Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Oct. 01, 2017	Sep. 25, 2016	Dec. 25, 2016
Acquired finite-lived intangible assets:
Gross Value	$ 110.9		$ 111.1
Accumulated Amortization	(93.3)		(85.4)
Net Value	17.6		25.7
Total intangible assets: Gross Value	117.8		118.0
Total intangible assets: Net Value	24.5		32.6
Aggregate amortization expense for finite-lived intangible assets	7.9	$ 7.9
Trade names
Acquired finite-lived intangible assets:
Indefinite-lived trade names	6.9		6.9
Customer relationships
Acquired finite-lived intangible assets:
Gross Value	53.7		53.7
Accumulated Amortization	(48.9)		(44.9)
Net Value	4.8		8.8
Contracts and backlog
Acquired finite-lived intangible assets:
Gross Value	30.8		30.8
Accumulated Amortization	(25.2)		(23.7)
Net Value	5.6		7.1
Developed technology and technical know-how
Acquired finite-lived intangible assets:
Gross Value	25.0		25.2
Accumulated Amortization	(17.9)		(15.7)
Net Value	7.1		9.5
Trade names
Acquired finite-lived intangible assets:
Gross Value	1.4		1.4
Accumulated Amortization	(1.3)		(1.1)
Net Value	$ 0.1		$ 0.3