Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jul. 01, 2018	Apr. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ 730.9			$ 730.9			$ 720.8
Revenue	151.2		$ 147.9	294.2	$ 279.9
Remaining performance obligation	501.9			501.9
Contract assets, Net change		$ 21.2
Contract liabilities, Net change		$ (11.5)
Revenue recognized	18.5			29.5
Effect of Change Higher/(Lower)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	3.6			11.2
Cost of revenue	4.0			8.3
ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit						$ 721.0
ASC 606 | Effect of Change Higher/(Lower)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	(2.9)			(2.9)
Revenue	$ 3.6			$ 11.2
ASC 606 Adjustment | ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit						$ 0.2