Segment Information and Geographic Data - Summary Information by Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Segment Reporting Information [Line Items]
Net sales	$ 84,310	$ 88,293
Operating income	23,346	26,274
Americas
Segment Reporting Information [Line Items]
Net sales	36,940	35,193
Operating income	11,200	11,316
Europe
Segment Reporting Information [Line Items]
Net sales	20,363	21,054
Operating income	6,658	6,893
Greater China
Segment Reporting Information [Line Items]
Net sales	13,169	17,956
Operating income	5,314	6,908
Japan
Segment Reporting Information [Line Items]
Net sales	6,910	7,237
Operating income	3,014	3,082
Rest of Asia Pacific
Segment Reporting Information [Line Items]
Net sales	6,928	6,853
Operating income	$ 2,560	$ 2,575