Equity (Impact of Reclassifications from Accumulated Other Comprehensive Income on Earnings (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Jan. 01, 2017	Oct. 02, 2016	Jun. 26, 2016	Mar. 27, 2016	Dec. 27, 2015	Sep. 27, 2015	Oct. 01, 2017	Oct. 02, 2016	Sep. 27, 2015	Sep. 28, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 5,457.0				$ 5,890.7				$ 5,819.8	$ 5,457.0	$ 5,890.7	$ 5,819.8	$ 5,273.7
Amounts Reclassified from AOCI, Interest income and other, net										275.3	108.0	43.0
Amounts Reclassified from AOCI, Interest expense										(92.5)	(81.3)	(70.5)
Amounts Reclassified from AOCI, Revenue	5,698.3	$ 5,661.5	$ 5,294.0	$ 5,732.9	5,711.2	$ 5,238.0	$ 4,993.2	$ 5,373.5		22,386.8	21,315.9	19,162.7
Amounts Reclassified from AOCI, Cost of sales including occupancy costs										(9,038.2)	(8,511.1)	(7,787.5)
Gain resulting from acquisition of joint venture										0.0	0.0	390.6
Amounts Reclassified from AOCI, Tax (expense)/benefit										(1,432.6)	(1,379.7)	(1,143.7)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified, from AOCI, Total before tax										67.2	(78.2)	65.9
Amounts Reclassified from AOCI, Tax (expense)/benefit										(14.0)	11.8	(23.5)
Amounts Reclassified from AOCI, Net of tax										53.2	(66.4)	42.4
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Impact to accumulated other comprehensive income from purchase of noncontrolling interest												0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(2.5)				1.1				(0.1)	(2.5)	1.1	(0.1)	(0.4)
Amounts Reclassified from AOCI, Net of tax										3.0	(1.0)	(0.6)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified from AOCI, Interest income and other, net										(4.1)	1.6	1.0
Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Impact to accumulated other comprehensive income from purchase of noncontrolling interest												0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (4.1)				10.9				25.6	(4.1)	10.9	25.6	46.3
Amounts Reclassified from AOCI, Net of tax										(55.6)	67.4	(51.5)
Accumulated Net Investment Hedge Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Impact to accumulated other comprehensive income from purchase of noncontrolling interest												0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					1.3				1.3		1.3	1.3	3.2
Amounts Reclassified from AOCI, Net of tax										0.0	0.0	(4.6)
Accumulated Net Investment Hedge Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain resulting from acquisition of joint venture										0.0	0.0	7.2
Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Impact to accumulated other comprehensive income from purchase of noncontrolling interest												31.1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					$ (121.7)				(226.2)		(121.7)	(226.2)	$ (23.8)
Amounts Reclassified from AOCI, Net of tax										(0.6)	0.0	14.3
Translation Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified from AOCI, Interest income and other, net										0.6	0.0	(7.1)
Gain resulting from acquisition of joint venture										0.0	0.0	(7.2)
Interest Rate Contract [Member] | Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified from AOCI, Interest expense									$ 2.0	4.8	5.0	3.2
Cross-Currency Swap [Member] | Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified from AOCI, Interest income and other, net										57.2	(101.1)	46.2
Foreign Currency Contract - Other [Member] | Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified from AOCI, Revenue										3.0	4.9	14.0
Foreign Currency and Coffee Contracts [Member] | Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts Reclassified from AOCI, Cost of sales including occupancy costs										$ 5.7	$ 11.4	8.6
Starbucks Coffee Japan Ltd [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain resulting from acquisition of joint venture												$ 390.6
Preexisting ownership percentage									39.50%			39.50%