Earnings Per Share (Calculation of Net Earnings Per Common Share ("EPS") - Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Sep. 29, 2019	Sep. 30, 2018	Oct. 01, 2017
Earnings Per Share [Abstract]
Net earnings attributable to Starbucks	$ 802.9	$ 1,372.8	$ 663.2	$ 760.6	$ 755.8	$ 852.5	$ 660.1	$ 2,250.2	$ 3,599.2	$ 4,518.3	$ 2,884.7
Weighted average common shares and common stock units outstanding (for basic calculation)									1,221.2	1,382.7	1,449.5
Dilutive effect of outstanding common stock options and RSUs									12.0	11.9	12.0
Weighted average common and common equivalent shares outstanding (for diluted calculation)									1,233.2	1,394.6	1,461.5
Earnings Per Share, Basic									$ 2.95	$ 3.27	$ 1.99
Earnings Per Share, Diluted	$ 0.67	$ 1.12	$ 0.53	$ 0.61	$ 0.56	$ 0.61	$ 0.47	$ 1.57	$ 2.92	$ 3.24	$ 1.97