Summary of Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Numerator:
Net income	$ 20,065	$ 17,891
Denominator:
Weighted-average shares outstanding (in shares)	5,112,877	5,298,661
Effect of dilutive securities (in shares)	44,910	29,334
Weighted-average diluted shares (in shares)	5,157,787	5,327,995
Basic earnings per share (in dollars per share)	$ 3.92	$ 3.38
Diluted earnings per share (in dollars per share)	$ 3.89	$ 3.36