Subsequent Events - Additional Information (Detail) (Subsequent Event [Member], Dutch Auction [Member], USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended
	Apr. 22, 2013
Subsequent Event [Line Items]
Tender offer to purchase common stock	$ 100
Commencement date of tender offer	April 26, 2013
Expiry date of tender offer	May 24, 2013
Percentage of common shares outstanding	14.10%
Minimum [Member]
Subsequent Event [Line Items]
Sale of common stock price per share	$ 5.75
Maximum [Member]
Subsequent Event [Line Items]
Sale of common stock price per share	$ 6.25