Valuation and Qualifying Accounts - Schedule II Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Oct. 02, 2015
Allowance for doubtful accounts receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 24.2	$ 21.1	$ 20.2
Charged to Bad Debt Expense	43.0	3.4	1.1
Write-offs Adjustments Charged to Allowance	(4.1)	(0.3)	(0.2)
Balance at End of Period	63.1	24.2	21.1
Valuation allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	79.6	69.7	67.5
Increases	26.2	12.2	4.7
Deductions	0.0	(2.3)	(2.5)
Balance at End of Period	$ 105.8	$ 79.6	$ 69.7