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		6 Months Ended
	Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018
Numerator:
Net income	$ 11,561	$ 13,822	$ 31,526	$ 33,887
Denominator:
Weighted-average basic shares outstanding (in shares)	4,674,071	5,024,877	4,704,945	5,068,877
Effect of dilutive securities (in shares)	26,575	43,616	32,004	44,263
Weighted-average diluted shares (in shares)	4,700,646	5,068,493	4,736,949	5,113,140
Basic earnings per share (in dollars per share)	$ 2.47	$ 2.75	$ 6.70	$ 6.69
Diluted earnings per share (in dollars per share)	$ 2.46	$ 2.73	$ 6.66	$ 6.63