Subsequent Events - Additional Information (Detail) - USD ($)		9 Months Ended
	Oct. 27, 2015	Sep. 30, 2015	Sep. 30, 2014
Subsequent Event [Line Items]
Extraordinary cash dividends declared per common share			$ 0.50
Share repurchase new limit amount		$ 25,000,000
Share repurchase program expiration date		Dec. 31, 2016
Subsequent Event [Member]
Subsequent Event [Line Items]
Share repurchase new limit amount	$ 25,000,000
Share repurchase program expiration date	Dec. 31, 2016
Dividend Declared [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Cash dividend per share	$ 0.15
Date of payment to shareholders entitled to dividends	Dec. 28, 2015
Date of record of shareholders entitled to dividends	Dec. 14, 2015
Extraordinary Dividend [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Date of payment to shareholders entitled to dividends	Dec. 28, 2015
Date of record of shareholders entitled to dividends	Dec. 14, 2015
Extraordinary cash dividends declared per common share	$ 3