Goodwill and Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Dec. 25, 2016
Acquired finite-lived intangible assets:
Gross Value	$ 111.1		$ 111.1
Accumulated Amortization	(90.7)		(85.4)
Net Value	20.4		25.7
Total intangible assets: Gross Value	118.0		118.0
Total intangible assets: Net Value	27.3		32.6
Aggregate amortization expense for finite-lived intangible assets	5.4	$ 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	53.7		53.7
Accumulated Amortization	(47.6)		(44.9)
Net Value	6.1		8.8
Contracts and backlog
Acquired finite-lived intangible assets:
Gross Value	30.8		30.8
Accumulated Amortization	(24.7)		(23.7)
Net Value	6.1		7.1
Developed technology and technical know-how
Acquired finite-lived intangible assets:
Gross Value	25.2		25.2
Accumulated Amortization	(17.2)		(15.7)
Net Value	8.0		9.5
Trade names
Acquired finite-lived intangible assets:
Gross Value	1.4		1.4
Accumulated Amortization	(1.2)		(1.1)
Net Value	$ 0.2		$ 0.3