Goodwill and Other Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Acquired finite-lived intangible assets:
Gross Value	$ 110.9	$ 111.1
Accumulated Amortization	(95.8)	(85.4)
Total	15.1	25.7
Total intangible assets, Gross Value	117.8	118.0
Total intangible assets, Net Value	22.0	32.6
Aggregate amortization expense for finite-live intangible assets	10.4	10.5	$ 13.0
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	(50.2)	(44.9)
Total	3.5	8.8
Contracts and backlog
Acquired finite-lived intangible assets:
Gross Value	30.8	30.8
Accumulated Amortization	(25.7)	(23.7)
Total	5.1	7.1
Developed technology and technical know-how
Acquired finite-lived intangible assets:
Gross Value	25.0	25.2
Accumulated Amortization	(18.6)	(15.7)
Total	6.4	9.5
Trade names
Acquired finite-lived intangible assets:
Gross Value	1.4	1.4
Accumulated Amortization	(1.3)	(1.1)
Total	$ 0.1	$ 0.3