Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Jan. 31, 2015	Sep. 30, 2007
Class Of Stock [Line Items]
Repurchase authorization, shares			5,000,000	10,000,000
Cash dividends paid to common stockholders	$ 28	$ 28
Cash dividend paid per share	$ 0.44	$ 0.44
Noncontrolling interest dividends declared	$ 16	$ 13
Cash dividends paid to noncontrolling interests	$ 3	$ 11
2007 Share Repurchase Authorization [Member]
Class Of Stock [Line Items]
Common stock shares repurchased		925,700
January 2015 Share Repurchase Authorization [Member]
Class Of Stock [Line Items]
Common stock shares repurchased	1,700,676
Shares remaining available for repurchase under the current authorization	3,299,324