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. 28, 2019	Dec. 29, 2018
Numerator:
Net income	$ 22,236	$ 19,965
Denominator:
Weighted-average basic shares outstanding (in shares)	4,415,040	4,735,820
Effect of dilutive securities (in shares)	39,564	37,432
Weighted-average diluted shares (in shares)	4,454,604	4,773,252
Basic earnings per share (in dollars per share)	$ 5.04	$ 4.22
Diluted earnings per share (in dollars per share)	$ 4.99	$ 4.18