Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2018	Mar. 26, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ 723.2			$ 720.8
Revenue	143.0	$ 132.0
Cost of revenue	102.2	$ 95.9
Remaining performance obligation	551.8
ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit			$ 721.0
ASC 606 Adjustment | ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit			$ 0.2
Effect of Change Higher/(Lower)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	7.7
Cost of revenue	4.2
Effect of Change Higher/(Lower) | ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ (3.5)