Benefit Plans - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018 USD ($) shares	Apr. 01, 2017 USD ($)	Mar. 31, 2018 USD ($) shares	Apr. 01, 2017 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance under stock plans (in shares) | shares	270,000,000		270,000,000
Income tax benefit related to share-based compensation expense	$ 347	$ 424	$ 1,000	$ 889
Total unrecognized compensation cost related to RSUs and stock options	11,400		$ 11,400
Total unrecognized compensation cost related to RSUs and stock options, weighted-average recognition period			2 years 9 months
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs granted, vesting period			4 years
Number of shares of common stock issued per RSU upon vesting			1
Reduction in number of shares available for grant per share issued with respect to RSUs granted (in shares) | shares			2
Factor by which each RSU canceled or share withheld for taxes increases the number of shares available for grant			2
Fair value of vested RSUs as of vesting date	$ 457	$ 460	$ 3,600	$ 2,600