Stockholders' Equity - Share Repurchases in the Open Market (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Equity, Class of Treasury Stock [Line Items]
Total cost	$ 4,104	$ 1,796
Class A common stock
Equity, Class of Treasury Stock [Line Items]
Shares repurchased in the open market (in shares)	19	9
Average repurchase price per share (in dollars per share)	$ 210.32	$ 201.73
Total cost	$ 4,104	$ 1,796

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

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