Treasury Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended		72 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
Equity Class Of Treasury Stock [Line Items]
Common stock amount authorized under repurchase program, value	$ 109.2	$ 150.0
Stock repurchased during period, shares			906,285	930,225	5,117,937
Average stock price of shares repurchased			$ 13.23	$ 8.94	$ 7.97