Summary of Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Numerator:
Net income	$ 17,891	$ 18,361
Denominator:
Weighted-average shares outstanding (in shares)	5,298,661	5,558,930
Effect of dilutive securities (in shares)	29,334	35,197
Weighted-average diluted shares (in shares)	5,327,995	5,594,127
Basic earnings per share (in dollars per share)	$ 3.38	$ 3.30
Diluted earnings per share (in dollars per share)	$ 3.36	$ 3.28