Stockholders' Equity - Share Repurchases in the Open Market (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Equity, Class of Treasury Stock [Line Items]
Total cost	$ 2,216	$ 2,949	$ 5,331	$ 7,053
Class A common stock
Equity, Class of Treasury Stock [Line Items]
Shares repurchased in the open market (in shares)	10	15	26	34
Average repurchase cost per share (in dollars per share)	$ 221.32	$ 210.18	$ 206.88	$ 210.26
Total cost	$ 2,216	$ 2,949	$ 5,331	$ 7,053

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).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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-Publisher FASB
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Balance Type:	debit
Period Type:	duration