Condensed Consolidated Financial Statement Details - Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 80,502	$ 75,076
Accumulated depreciation and amortization	(45,425)	(41,293)
Total property, plant and equipment, net	35,077	33,783
Land and buildings
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	14,931	13,587
Machinery, equipment and internal-use software
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	57,784	54,210
Leasehold improvements
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 7,787	$ 7,279