Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	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	$ 14,000,000	$ 14,000,000
Cash dividend paid per share	$ 0.22	$ 0.22
Dividend declared but not paid	$ 0
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	1,594,300
Shares remaining available for repurchase under the current authorization	3,405,700