Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Oct. 01, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 25, 2016	Sep. 25, 2016	Jun. 26, 2016	Mar. 27, 2016	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Condensed Financial Statements, Captions [Line Items]
Service revenues									$ 346.4	$ 348.1	$ 354.2
Product sales									405.5	320.6	302.9
Total revenues	$ 202.2	$ 196.2	$ 185.7	$ 167.8	$ 182.1	$ 165.4	$ 168.2	$ 153.0	751.9	668.7	657.1
Cost of service revenues									247.5	255.8	266.5
Cost of product sales									307.1	259.3	228.8
Total costs									554.6	515.1	495.3
Gross profit	56.7	48.1	47.4	45.1	46.6	25.9	45.2	35.9	197.3	153.6	161.8
Selling, general and administrative expenses									185.3	158.3	150.1
Research and development expenses									17.8	13.9	16.2
Operating loss from continuing operations	(13.2)	3.1	2.6	1.7	4.6	(13.0)	0.0	(10.2)	(5.8)	(18.6)	(4.5)
Other income (expense):
Interest income (expense), net									(28.6)	(34.7)	(36.0)
Gain (loss) on extinguishment of debt									(17.3)	0.2	(3.4)
Other income (expense), net									0.9	0.8	(0.7)
Total other expense, net									(45.0)	(33.7)	(40.1)
Loss from continuing operations before income taxes									(50.8)	(52.3)	(44.6)
Provision (benefit) for income taxes from continuing operations	(11.7)	0.2	1.8	1.5	0.8	1.9	1.8	3.6	(8.2)	8.1	(11.4)
Income (loss) from continuing operations									(42.6)	(60.4)	(33.2)
Loss from discontinued operations									(0.1)	(0.1)	53.0
Equity in net income (loss) of subsidiaries									0.0	0.0	0.0
Net income (loss)	$ (22.2)	$ (4.3)	$ (6.2)	$ (10.0)	$ (4.3)	$ (23.6)	$ (10.4)	$ (22.2)	(42.7)	(60.5)	19.8
Comprehensive income (loss)									(42.4)	(60.8)	20.1
Eliminations
Condensed Financial Statements, Captions [Line Items]
Service revenues									0.0	0.0	0.0
Product sales									(14.7)	(7.8)	(15.7)
Total revenues									(14.7)	(7.8)	(15.7)
Cost of service revenues									0.0	0.0	0.0
Cost of product sales									(14.7)	(7.8)	(15.7)
Total costs									(14.7)	(7.8)	(15.7)
Gross profit									0.0	0.0	0.0
Selling, general and administrative expenses									0.0	0.0	0.0
Research and development expenses									0.0	0.0	0.0
Operating loss from continuing operations									0.0	0.0	0.0
Other income (expense):
Interest income (expense), net									0.0	0.0	0.0
Gain (loss) on extinguishment of debt									0.0	0.0	0.0
Other income (expense), net									0.0	0.0	0.0
Total other expense, net									0.0	0.0	0.0
Loss from continuing operations before income taxes									0.0	0.0	0.0
Provision (benefit) for income taxes from continuing operations									0.0	0.0	0.0
Income (loss) from continuing operations									0.0	0.0	0.0
Loss from discontinued operations									0.0	0.0	0.0
Equity in net income (loss) of subsidiaries									(15.6)	12.6	8.3
Net income (loss)									(15.6)	12.6	8.3
Comprehensive income (loss)									(15.9)	12.9	8.2
Parent Company
Condensed Financial Statements, Captions [Line Items]
Service revenues									0.0	0.0	0.0
Product sales									0.0	0.0	0.0
Total revenues									0.0	0.0	0.0
Cost of service revenues									0.0	0.0	0.0
Cost of product sales									0.0	0.0	0.0
Total costs									0.0	0.0	0.0
Gross profit									0.0	0.0	0.0
Selling, general and administrative expenses									9.1	6.3	10.1
Research and development expenses									0.0	0.0	0.0
Operating loss from continuing operations									(9.1)	(6.3)	(10.1)
Other income (expense):
Interest income (expense), net									(28.9)	(34.6)	(35.8)
Gain (loss) on extinguishment of debt									(17.3)	0.2	(3.4)
Other income (expense), net									0.0	0.0	0.0
Total other expense, net									(46.2)	(34.4)	(39.2)
Loss from continuing operations before income taxes									(55.3)	(40.7)	(49.3)
Provision (benefit) for income taxes from continuing operations									0.4	(0.1)	(17.8)
Income (loss) from continuing operations									(55.7)	(40.6)	(31.5)
Loss from discontinued operations									(0.1)	(0.1)	71.8
Equity in net income (loss) of subsidiaries									13.1	(19.8)	(20.5)
Net income (loss)									(42.7)	(60.5)	19.8
Comprehensive income (loss)									(42.4)	(60.8)	20.1
Subsidiary Guarantors on a Combined Basis
Condensed Financial Statements, Captions [Line Items]
Service revenues									334.3	330.9	339.0
Product sales									360.2	273.8	262.3
Total revenues									694.5	604.7	601.3
Cost of service revenues									238.6	244.0	255.5
Cost of product sales									274.4	225.0	203.1
Total costs									513.0	469.0	458.6
Gross profit									181.5	135.7	142.7
Selling, general and administrative expenses									163.6	142.3	130.8
Research and development expenses									16.6	13.5	15.7
Operating loss from continuing operations									1.3	(20.1)	(3.8)
Other income (expense):
Interest income (expense), net									0.2	(0.1)	(0.1)
Gain (loss) on extinguishment of debt									0.0	0.0	0.0
Other income (expense), net									0.2	0.2	(3.3)
Total other expense, net									0.4	0.1	(3.4)
Loss from continuing operations before income taxes									1.7	(20.0)	(7.2)
Provision (benefit) for income taxes from continuing operations									(8.9)	7.0	4.4
Income (loss) from continuing operations									10.6	(27.0)	(11.6)
Loss from discontinued operations									0.0	0.0	(21.1)
Equity in net income (loss) of subsidiaries									2.5	7.2	12.2
Net income (loss)									13.1	(19.8)	(20.5)
Comprehensive income (loss)									13.1	(19.8)	(20.5)
Non-Guarantors on a Combined Basis
Condensed Financial Statements, Captions [Line Items]
Service revenues									12.1	17.2	15.2
Product sales									60.0	54.6	56.3
Total revenues									72.1	71.8	71.5
Cost of service revenues									8.9	11.8	11.0
Cost of product sales									47.4	42.1	41.4
Total costs									56.3	53.9	52.4
Gross profit									15.8	17.9	19.1
Selling, general and administrative expenses									12.6	9.7	9.2
Research and development expenses									1.2	0.4	0.5
Operating loss from continuing operations									2.0	7.8	9.4
Other income (expense):
Interest income (expense), net									0.1	0.0	(0.1)
Gain (loss) on extinguishment of debt									0.0	0.0	0.0
Other income (expense), net									0.7	0.6	2.6
Total other expense, net									0.8	0.6	2.5
Loss from continuing operations before income taxes									2.8	8.4	11.9
Provision (benefit) for income taxes from continuing operations									0.3	1.2	2.0
Income (loss) from continuing operations									2.5	7.2	9.9
Loss from discontinued operations									0.0	0.0	2.3
Equity in net income (loss) of subsidiaries									0.0	0.0	0.0
Net income (loss)									2.5	7.2	12.2
Comprehensive income (loss)									$ 2.8	$ 6.9	$ 12.3