Organization and Summary of Significant Accounting Policies - Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 30, 2018	Dec. 31, 2017	Dec. 25, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ 724.5				$ 720.8				$ 724.5	$ 720.8
Revenue	164.4	$ 159.4	$ 151.2	$ 143.0	166.3	$ 157.1	$ 147.9	$ 132.0	618.0	603.3	$ 541.9
Remaining performance obligation	620.7								620.7
Provision for loss on contracts	5.1				10.3				5.1	10.3
Contract assets, Net change									33.5
Contract liabilities, Net change									(9.8)
Revenue recognized									35.5
Unbilled
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable	3.8				$ 1.9				3.8	$ 1.9
Effect of Change Higher/(Lower)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									30.0
Cost of revenue									21.9
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	$ (8.1)								(8.1)
Revenue									$ 30.0
ASC 606 Adjustment | ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit												$ 0.2