Income Taxes - Tax Effect of Temporary Differences that Give Rise to Significant Portions of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Deferred Tax Assets:
Accrued compensation and benefits	$ 172	$ 166
Accrued litigation obligation	331	234
Client incentives	442	327
Net operating loss carryforwards	117	104
Comprehensive loss	21	106
Federal benefit of state taxes	133	157
Other	71	55
Valuation allowance	(120)	(103)
Deferred tax assets	1,167	1,046
Deferred Tax Liabilities:
Property, equipment and technology, net	(450)	(346)
Intangible assets	(5,788)	(6,452)
Unrealized gains on equity securities	(124)	(203)
Foreign taxes	(50)	(93)
Deferred tax liabilities	(6,412)	(7,094)
Net deferred tax liabilities	$ (5,245)	$ (6,048)