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		9 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Numerator:
Net income	$ 11,519	$ 8,717	$ 45,406	$ 37,637
Denominator:
Weighted-average basic shares outstanding (in shares)	4,882,167	5,195,088	5,006,640	5,239,847
Effect of dilutive securities (in shares)	44,442	38,411	44,323	34,547
Weighted-average diluted shares (in shares)	4,926,609	5,233,499	5,050,963	5,274,394
Basic earnings per share (in dollars per share)	$ 2.36	$ 1.68	$ 9.07	$ 7.18
Diluted earnings per share (in dollars per share)	$ 2.34	$ 1.67	$ 8.99	$ 7.14