Earnings Per Share - Additional Information (Detail) (USD $)	1 Months Ended	11 Months Ended
	Oct. 25, 2011	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock repurchase program, authorized amount	$ 250,000,000
Shares repurchased under repurchase program		13,986,349
Shares repurchased under repurchase program, value		$ 107,304,000
Shares repurchased average price per share		$ 7.67
Maximum
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock repurchase program, expiration year	2013-04