Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 30, 2018	Dec. 31, 2017	Oct. 01, 2018	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Tax Assets, Net, Noncurrent	$ 650.0		$ 123.7	$ 134.7
Deferred Revenue, Current	1,554.2		1,221.0	1,642.9
Income Tax Expense (Benefit)	$ 205.1	$ 755.8
Earnings per share - diluted	$ 0.61	$ 1.57
Earnings Per Share, Basic	$ 0.61	$ 1.58
Deferred Revenue, Noncurrent	$ 6,823.7		6,840.0	6,775.7
Deferred Tax and Other Liabilities, Noncurrent	1,478.2		1,509.5	1,430.5
Retained Earnings (Accumulated Deficit)	(2,584.0)		$ 1,725.0	1,457.4
Accounting Standards Update 2016-16 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	227.6
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Tax Assets, Net, Noncurrent				(11.0)
Deferred Revenue, Current				(422.0)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 268.0
Deferred Revenue, Noncurrent				64.0
Deferred Tax and Other Liabilities, Noncurrent				79.0
Retained Earnings (Accumulated Deficit)				$ 268.0