Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss			$ (25.5)
Changes in foreign currency translation adjustment	$ 2.4	$ 10.1	(0.8)	$ 15.6
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent	0.0		0.0	0.6
Changes in value of hedged interest rate caps, net of tax of $0.3 and $0.8 for the three and six months ended March 30, 2019 and $0.3 and $(4.6) for the three and six months ended March 31, 2018:	(1.5)	0.7	(5.4)	(3.6)
Accumulated other comprehensive loss	(30.5)		(30.5)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(29.8)	(13.0)	(26.6)	(18.5)
Changes in foreign currency translation adjustment	2.4	10.1	(0.8)	15.6
Amounts reclassified to statement of income	0.0	0.0	0.0	0.0
Accumulated other comprehensive loss	(27.4)	(2.9)	(27.4)	(2.9)
Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss				(0.4)
Changes in unrealized holding gains and losses on available-for-sale securities, net of tax of$0.2 for the three months ended December 30, 2017:				0.0
Amounts reclassified to statement of income				0.4
Accumulated other comprehensive loss		0.0		0.0
Pension Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(1.1)	(1.0)	(1.1)	(1.6)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent	0.0	0.0	0.0	(0.6)
Amounts reclassified to statement of income	0.0	0.0	0.0	0.0
Accumulated other comprehensive loss	(1.1)	(1.0)	(1.1)	(1.0)
Hedged Interest Rate Caps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(1.0)	2.3	2.2	4.3
Changes in value of hedged interest rate caps, net of tax of $0.3 and $0.8 for the three and six months ended March 30, 2019 and $0.3 and $(4.6) for the three and six months ended March 31, 2018:	(1.5)	0.7	(5.4)	(3.6)
Amounts reclassified to statement of income	0.5	0.3	1.2	2.6
Accumulated other comprehensive loss	(2.0)	3.3	(2.0)	3.3
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(31.9)	(11.7)	(25.5)	(16.2)
Other Comprehensive Income (Loss) before Reclassifications, Tax	0.9	10.8	(6.2)	12.6
Amounts reclassified to statement of income	0.5	0.3	1.2	3.0
Accumulated other comprehensive loss	$ (30.5)	$ (0.6)	$ (30.5)	$ (0.6)