Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Apr. 01, 2018	Mar. 31, 2019	Apr. 01, 2018	Dec. 30, 2018	Oct. 01, 2018	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Tax Assets, Net, Noncurrent	$ 1,006.6		$ 1,006.6			$ 123.7	$ 134.7
Deferred Revenue, Current	1,311.4		1,311.4			1,220.9	1,642.9
Income Tax Expense (Benefit)	$ 161.2	$ 155.8	$ 366.4	$ 911.6
Earnings per share - diluted	$ 0.53	$ 0.47	$ 1.14	$ 2.05
Earnings Per Share, Basic	$ 0.54	$ 0.47	$ 1.15	$ 2.07
Deferred Revenue, Noncurrent	$ 6,761.9		$ 6,761.9			6,839.7	6,775.7
Deferred Tax and Other Liabilities, Noncurrent	1,500.3		1,500.3			1,509.5	1,430.5
Retained Earnings (Accumulated Deficit)	$ (4,807.7)		$ (4,807.7)			$ 1,725.4	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