Tax Effect of Temporary Differences that Give Rise to Significant Portions of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Deferred Tax Assets
Accrued compensation and benefits	$ 194	$ 277
Comprehensive loss	29	106
Accrued litigation obligation	373	373
Client incentives	272	266
Net operating loss carryforwards	45	32
Federal benefit of state taxes	236	195
Federal benefit of foreign taxes	0	1,214
Other	193	280
Valuation allowance	35	31
Deferred tax assets	1,307	2,712
Deferred Tax Liabilities
Property, equipment and technology, net	(391)	(278)
Intangible assets	(6,756)	(7,013)
Foreign taxes	(59)	(106)
Other	0	(101)
Deferred tax liabilities	(7,206)	(7,498)
Net deferred tax liabilities	$ (5,899)	$ (4,786)