Summary of Significant Accounting Policies - Operating Income from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2018	Mar. 26, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Service revenues	$ 46.0	$ 49.2
Product sales	97.0	82.8
Total revenues	143.0	132.0
Cost of service revenues	32.9	35.0
Cost of product sales	69.3	60.9
Total costs	102.2	95.9
Gross profit	40.8	36.1
Selling, general and administrative expenses	29.8	30.0
Operating income from continuing operations	7.0	$ 1.4
Balances Without Adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Service revenues	46.0
Product sales	89.3
Total revenues	135.3
Cost of service revenues	32.9
Cost of product sales	65.1
Total costs	98.0
Gross profit	37.3
Selling, general and administrative expenses	29.8
Operating income from continuing operations	3.5
Effect of Change Higher/(Lower)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Service revenues	0.0
Product sales	7.7
Total revenues	7.7
Cost of service revenues	0.0
Cost of product sales	4.2
Total costs	4.2
Gross profit	3.5
Selling, general and administrative expenses	0.0
Operating income from continuing operations	$ 3.5