Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	9 Months Ended	12 Months Ended
	Jan. 22, 2009	Sep. 30, 2013	Dec. 31, 2009	Dec. 31, 2012
Equity [Abstract]
Preferred stock, shares outstanding		0		0
Authorization for purchase of company's Common stock	$ 10.0
Purchase Common stock shares		0	349,800
Average cost of per share			$ 2.67
Purchase Common stock value			$ 0.9