Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Jan. 31, 2015
Class Of Stock [Line Items]
Repurchase authorization, shares			5,000,000
Cash dividends paid to common stockholders	$ 38	$ 28
Cash dividend paid per share	$ 0.60	$ 0.44
Noncontrolling interest dividends declared	$ 14	$ 16
Dividends paid to noncontrolling interests	$ 2	$ 3
January 2015 Share Repurchase Authorization [Member]
Class Of Stock [Line Items]
Common stock shares repurchased	2,684,176
Shares remaining available for repurchase under the current authorization	2,315,824