Accumuated Other Comprehensive Income Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 25, 2016	Jun. 27, 2015	Jun. 25, 2016	Jun. 27, 2015	Mar. 26, 2016	Sep. 26, 2015	Mar. 28, 2015	Sep. 27, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in foreign currency translation adjustment	$ (3.8)	$ 4.5	$ (9.2)	$ (14.0)
Changes in unrealized holding gains and losses on available-for-sale securities:	0.0	(0.7)	(1.2)	(3.9)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent	0.0		0.0	(0.1)
Changes in value of hedged interest rate caps, net of tax of $0.9 and $2.1 for the three and nine months ended June 25, 2016 and $0.5 and $1.4 for the three and nine months ended June 27, 2015:	(1.5)	(0.7)	(3.4)	(2.3)
Other Comprehensive Income (Loss) before Reclassifications, Tax	(5.3)	3.1	(13.8)	(20.1)
Restructuring Reserve, Translation and Other Adjustment	1.2	9.6	(5.0)	9.6
Accumulated other comprehensive loss	(33.3)	(7.9)	(33.3)	(7.9)	$ (29.2)	$ (14.5)	$ (20.6)	$ 2.6
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in foreign currency translation adjustment	(3.8)	4.5	(9.2)	(14.0)
Restructuring Reserve, Translation and Other Adjustment	0.0	9.6	0.0	9.6
Accumulated other comprehensive loss	(24.9)	(9.1)	(24.9)	(9.1)	(21.1)	(15.7)	(23.2)	(4.7)
Equity securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in unrealized holding gains and losses on available-for-sale securities:	0.0	(0.7)	(1.2)	(3.9)
Restructuring Reserve, Translation and Other Adjustment	0.0	0.0	(7.2)	0.0
Accumulated other comprehensive loss	(1.5)	5.0	(1.5)	5.0	(1.5)	6.9	5.7	8.9
Pension in Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent	0.0	0.0	0.0	(0.1)
Restructuring Reserve, Translation and Other Adjustment	0.0	0.0	0.0	0.0
Accumulated other comprehensive loss	(1.8)	(1.5)	(1.8)	(1.5)	(1.8)	(1.8)	(1.5)	(1.6)
Interest rate cap - derivative
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in value of hedged interest rate caps, net of tax of $0.9 and $2.1 for the three and nine months ended June 25, 2016 and $0.5 and $1.4 for the three and nine months ended June 27, 2015:	(1.5)	(0.7)	(3.4)	(2.3)
Restructuring Reserve, Translation and Other Adjustment	1.2	0.0	2.2	0.0
Accumulated other comprehensive loss	$ (5.1)	$ (2.3)	$ (5.1)	$ (2.3)	$ (4.8)	$ (3.9)	$ (1.6)	$ 0.0