Shareholders' Equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Stockholders' Equity Note [Abstract]
Income tax (benefit) provision for net (losses) gains recorded in other comprehensive income for defined benefit pension, postretirement plans and postemployment plans	$ (47,000,000)	$ (86,000,000)	$ 121,000,000
Tax benefits associated with reclassification adjustments	23,000,000	17,000,000	$ 30,000,000
Other comprehensive income (loss), derivatives qualifying as hedges, tax	$ (10,000,000)	$ 0