Inventories - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Inventory Disclosure [Abstract]
Inventory valued under the LIFO method	6.00%	5.00%
Inventory, LIFO reserve	$ 30	$ 52
Increase (Decrease) in cost of sales	1	0	$ (1)
Effect of LIFO inventory liquidation on income	$ (1)	$ 0	$ 1
Liquidation of LIFO inventory, resulted per diluted common share	$ 0.01	$ 0.00	$ 0.01
Obsolete inventory reserve	$ 20	$ 14
Lower of cost or market reserve inventory	$ 6