Stockholders' Deficit - Narrative (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($) vote $ / shares shares	Jun. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) vote $ / shares	Sep. 30, 2023 USD ($) $ / shares	Mar. 31, 2024 USD ($)	Jul. 31, 2024 USD ($)
Accelerated Share Repurchases [Line Items]
Number of votes per share of common stock permitted on proposals presented to stockholders (vote) | vote	1				1
Dividends declared per common share (in dollars per share) | $ / shares	$ 0.71	$ 0.62	$ 0.62		$ 1.33	$ 1.16
Other accrued liabilities	$ 4,787				$ 4,787		$ 4,915
Excise taxes					41		$ 25
Authorized repurchase amount (up to)								$ 4,000
Authorized amount available for future repurchases	$ 8,600				8,600
Open Market Share Repurchase Transactions
Accelerated Share Repurchases [Line Items]
Common stock repurchased (in shares) | shares	2.9	1.0	2.0	1.8
Shares repurchased	$ 1,500	$ 528	$ 840	$ 673
Average price of shares repurchased (in usd per share) | $ / shares	$ 533.46	$ 548.20	$ 422.39	$ 379.14
Other accrued liabilities	$ 22		$ 23		22	$ 23
Excise taxes	$ 15		$ 8		$ 16	$ 12