Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Prepaid Expenses and Other Assets [Abstract]
Prepaid operating expenses and maintenance	$ 151	$ 137
Income tax receivable (See Note 19—Income Taxes)	232	77
Foreign exchange derivative instruments (See Note 12—Derivative Financial Instruments)	50	76
Other	122	63
Total	$ 555	$ 353