Accumulated Other Comprehensive (Loss) Income - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax expense (benefits) associated with reclassification adjustments	$ (23,000,000)	$ 97,000,000	$ 35,000,000	$ 261,000,000
Income tax benefits recorded for losses recognized in other comprehensive income relating to cash flow hedges	(2,000,000)	0	(8,000,000)	0
Benefit Plans Adjustments [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax expense (benefits) associated with reclassification adjustments	$ (6,000,000)	$ (4,000,000)	$ (17,000,000)	$ (13,000,000)