Financial Statements - Carrying Amounts and Classification of Assets and Liabilities for Consolidated VIEs (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015
Variable Interest Entity [Line Items]
Current assets	$ 11,847	$ 10,469	$ 12,459
Current liabilities	12,886	10,446	12,066
Noncurrent liabilities	8,219	8,398	8,760
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Current assets	265	281	252
Noncurrent assets	123	128	131
Total assets	388	409	383
Current liabilities	200	232	206
Noncurrent liabilities	31	34	35
Total liabilities	$ 231	$ 266	$ 241