Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2017		Sep. 30, 2016	Oct. 02, 2015
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 0.5		$ 0.4	$ 0.8
Charged to Cost and Expenses	0.2		0.1	0.0
Deductions	(0.2)		0.0	(0.4)
Misc.	0.0	[1]	0.0	0.0	[1]
Ending Balance	0.5		0.5	0.4
Allowance for Sales Returns [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	12.3		12.2	14.1
Charged to Cost and Expenses	10.8		16.1	16.0
Deductions	(8.4)		(16.0)	(17.9)
Misc.	0.0	[1]	0.0	0.0	[1]
Ending Balance	14.7		12.3	12.2
Valuation Allowance of Deferred Tax Assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	79.1		65.2	60.8
Charged to Cost and Expenses	11.8		13.9	3.6
Deductions	0.0		0.0	0.0
Misc.	0.0	[1]	0.0	0.8	[1]
Ending Balance	$ 90.9		$ 79.1	$ 65.2

[1] Includes acquired balances