Segment Information and Geographic Data - Net Sales by Product (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Segment Reporting Information [Line Items]
Net sales	$ 62,900	$ 53,265	$ 61,137	$ 88,293	$ 52,579	$ 45,408	$ 52,896	$ 78,351	$ 265,595	$ 229,234	$ 215,639
iPhone
Segment Reporting Information [Line Items]
Net sales									166,699	141,319	136,700
iPad
Segment Reporting Information [Line Items]
Net sales									18,805	19,222	20,628
Mac
Segment Reporting Information [Line Items]
Net sales									25,484	25,850	22,831
Services
Segment Reporting Information [Line Items]
Net sales									37,190	29,980	24,348
Services | Favorable final resolution of various lawsuits
Segment Reporting Information [Line Items]
Net sales									236
Services | Change in estimate based on the availability of additional supporting information
Segment Reporting Information [Line Items]
Net sales										640
Other Products
Segment Reporting Information [Line Items]
Net sales									$ 17,417	$ 12,863	$ 11,132