Income Taxes - Deferred Income Taxes (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Compensation and benefits, assets	$ 720	$ 647
Loss and credit carryforwards, assets	1,101	538
Other, assets	720	634
Deferred income taxes, assets, gross	2,541	1,819
Valuation allowance, assets	(997)	(452)
Deferred income taxes, assets	1,544	1,367
Property and equipment, liabilities	235	156
Deferred Tax Liabilities, Other Finite-Lived Assets	1,493	2,033
Other, liabilities	607	606
Deferred income taxes, liabilities, gross	2,336	2,795
Deferred income taxes, liabilities	$ 2,336	$ 2,795