Summary of Significant Accounting Policies - Operating Income from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 151.2	$ 147.9	$ 294.2	$ 279.9
Total costs	111.9	110.4	214.1	206.3
Gross profit	39.3	37.5	80.1	73.6
Selling, general and administrative expenses	30.1	31.9	59.9	61.9
Operating income from continuing operations	2.6	1.5	9.6	2.9
Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	47.0	53.8	93.0	103.0
Total costs	33.2	39.1	66.1	74.1
Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	104.2	94.1	201.2	176.9
Total costs	78.7	$ 71.3	148.0	$ 132.2
Balances Without Adoption of ASC 606 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	147.6		283.0
Total costs	107.9		205.8
Gross profit	39.7		77.2
Selling, general and administrative expenses	30.1		59.9
Operating income from continuing operations	3.0		6.7
Balances Without Adoption of ASC 606 | ASC 606 | Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	47.0		93.0
Total costs	33.2		66.1
Balances Without Adoption of ASC 606 | ASC 606 | Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	100.6		190.0
Total costs	74.7		139.7
Effect of Change Higher/(Lower)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	3.6		11.2
Effect of Change Higher/(Lower) | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	3.6		11.2
Total costs	4.0		8.3
Gross profit	(0.4)		2.9
Selling, general and administrative expenses	0.0		0.0
Operating income from continuing operations	(0.4)		2.9
Effect of Change Higher/(Lower) | ASC 606 | Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	0.0		0.0
Total costs	0.0		0.0
Effect of Change Higher/(Lower) | ASC 606 | Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	3.6		11.2
Total costs	$ 4.0		$ 8.3