Treasury Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		75 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Equity Class Of Treasury Stock [Line Items]
Common stock amount authorized under repurchase program, value	$ 109.2	$ 150.0
Stock repurchased during period, shares			161,200	5,117,937
Average stock price of shares repurchased			$ 13.08	$ 7.97