Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Jun. 28, 2013	Sep. 28, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 35.1	$ 44.6
Corporate debt security	59.5	49.7
Derivative assets	1.1	0.8
Option to purchase a company	1.4	1.4
Total assets measured at fair value	97.4	97.6
Contingent consideration	(7.6)	(8.8)
Total liabilities measured at fair value	(7.6)	(8.8)
Short-term investment	59.5	49.7
Prepaid expenses and other current assets	1.1	0.8
Other assets	1.7	2.5
Accrued liabilities	(1.7)	(1.6)
Other long-term liabilities	(5.9)	(7.2)
Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	35.4	45.7
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	35.1	44.6
Total assets measured at fair value	35.4	45.7
Other assets	0.3	1.1
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	35.4	45.7
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	1.1	0.8
Total assets measured at fair value	1.1	0.8
Prepaid expenses and other current assets	1.1	0.8
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Corporate debt security	59.5	49.7
Option to purchase a company	1.4	1.4
Total assets measured at fair value	60.9	51.1
Contingent consideration	(7.6)	(8.8)
Total liabilities measured at fair value	(7.6)	(8.8)
Short-term investment	59.5	49.7
Other assets	1.4	1.4
Accrued liabilities	(1.7)	(1.6)
Other long-term liabilities	$ (5.9)	$ (7.2)