Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jul. 31, 2018	Jan. 31, 2015
Class Of Stock [Line Items]
Repurchase authorization, shares				5,000,000
Cash dividends paid to common stockholders	$ 60	$ 57
Cash dividend paid per share	$ 0.96	$ 0.915
Dividends paid to noncontrolling interests	$ 21	$ 13
Subsequent Event [Member]
Class Of Stock [Line Items]
Repurchase authorization, shares			10,000,000
January 2015 Share Repurchase Authorization [Member]
Class Of Stock [Line Items]
Common stock shares repurchased under the current authorization	4,171,802
Shares remaining available for repurchase under the current authorization	828,198