Summary of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Millions		3 Months Ended		12 Months Ended
	Apr. 09, 2015 USD ($) $ / shares	Jul. 02, 2017 USD ($)	Dec. 28, 2014 USD ($)	Oct. 01, 2017 USD ($) $ / shares	Oct. 02, 2016 USD ($) $ / shares	Sep. 27, 2015 USD ($)
Accounting Policies [Abstract]
Stored Value Cards and Loyalty Program				$ 104.6	$ 60.5	$ 39.3
Number of reportable operating segments				4
Derivative [Line Items]
Goodwill, Impairment Loss				$ 87.2	0.0	0.0
Derivative asset, cash collateral				5.8
Derivative, Collateral, Obligation to Return Cash					19.5
Derivative contract, potential effects of netting, reduction in value				7.4	9.4
Derivative asset				30.4	25.0
Derivative liability				31.1	80.2
Receivables, net of Allowance for Doubtful Accounts
Allowance for doubtful accounts				9.8	9.4
Inventories
Inventory reserves				38.4	39.6
Property, Plant and Equipment [Line Items]
Excess Tax Benefit from Share-based Compensation, Operating Activities				77.5	122.8	132.4
Net disposition charges on property, plant and equipment				(46.9)	(25.1)	(12.5)
Net impairment charges on property, plant and equipment				56.1	24.1	25.8
Other Intangible Assets
Other intangible asset impairment charges			$ 0.0	0.0	0.0
Marketing & Advertising
Advertising expenses				282.6	248.6	$ 227.9
Asset Retirement Obligations
Net ARO assets included in property, plant and equipment				12.4	9.3
Net ARO liabilities included in other long-term liabilities				$ 70.0	$ 67.9
Class of Stock [Line Items]
Common stock, par value | $ / shares				$ 0.001	$ 0.001
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment, in years				2 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment, in years				15 years
Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment, in years				30 years
Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment, in years				40 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property, plant and equipment, in years				10 years
Commodity Contract [Member] | Maximum [Member]
Derivative [Line Items]
Derivative instruments maturity, in years				3 years
Teavana [Member]
Derivative [Line Items]
Goodwill, Impairment Loss		$ 69.3
Starbucks Coffee Switzerland [Member]
Derivative [Line Items]
Goodwill, Impairment Loss		$ 17.9
Restructuring Charges [Member]
Property, Plant and Equipment [Line Items]
Net impairment charges on property, plant and equipment				$ 39.9
Common Stock [Member]
Class of Stock [Line Items]
Stock split conversion ratio	2
Common stock, par value | $ / shares	$ 0.001
Impact to shareholders' equity from stock split	$ 0.0