Stockholders' Equity - Additional Information (Detail) (USD $)	0 Months Ended			12 Months Ended									0 Months Ended			0 Months Ended			12 Months Ended
	Jun. 30, 2013	Sep. 05, 2012	Aug. 06, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Sep. 05, 2012	Jun. 30, 2012	Aug. 06, 2012 Maximum [Member]	Aug. 06, 2012 Minimum [Member]	Nov. 30, 2007 November 2007 authorization plan [Member]	Jun. 30, 2013 May 2012 authorization plan [Member]	May 31, 2012 May 2012 authorization plan [Member]	Jan. 28, 2013 January 2013 authorization plan [Member]	Sep. 30, 2013 July 2013 authorization plan [Member]	Sep. 30, 2013 July 2013 authorization plan [Member]	Jul. 29, 2013 July 2013 authorization plan [Member]	Sep. 30, 2013 Open Market Share Repurchase Program [Member]
Stockholders Equity [Line Items]
Stock repurchase program authorized amount												$ 35,000,000		$ 50,000,000	$ 10,000,000			$ 20,000,000
Amount available for repurchases of shares									55,300,000								11,500,000
Amount of tender offer for repurchases of shares			55,000,000
Share price in tender offer								$ 19.00		$ 19.00	$ 17.00
Common stock repurchased, Shares		2,894,253		485,777	795,643	2,894,253										390,353
Common stock repurchased		$ 55,000,000		$ 11,541,000	$ 18,809,000	$ 54,991,000							$ 300,000						$ 1,000,000
Number of cumulative shares repurchased						1,303,240	405,290
Stock repurchased average price per share	$ 25.47			$ 23.77		$ 26.86										$ 21.71