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. 29, 2018	Dec. 30, 2017
Numerator:
Net income	$ 19,965	$ 20,065
Denominator:
Weighted-average basic shares outstanding (in shares)	4,735,820	5,112,877
Effect of dilutive securities (in shares)	37,432	44,910
Weighted-average diluted shares (in shares)	4,773,252	5,157,787
Basic earnings per share (in dollars per share)	$ 4.22	$ 3.92
Diluted earnings per share (in dollars per share)	$ 4.18	$ 3.89