Derivative Financial Instruments - Significant Assumptions Utilized in Binomial Lattice Process (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Level 1 [Member]
Derivative [Line Items]
Linked common shares	1,725,000	1,800,000	1,725,000
Quoted market price on valuation date	$ 3.00	$ 3.15	$ 2.97
Contractual exercise rate	$ 2.4648	$ 2.5000	$ 2.4648
Term (years)	11 days	1 year 11 days	9 months 11 days
Risk free rates using zero coupon US Treasury Security rates	0.03%
Level 1 [Member] | Minimum [Member]
Derivative [Line Items]
Range of market volatilities	24.00%	38.90%	33.10%
Risk free rates using zero coupon US Treasury Security rates		0.06%	0.02%
Level 1 [Member] | Maximum [Member]
Derivative [Line Items]
Range of market volatilities	31.50%	68.10%	49.17%
Risk free rates using zero coupon US Treasury Security rates		0.17%	0.11%
Level 2 [Member]
Derivative [Line Items]
Linked common shares	525,000	525,000	525,000
Quoted market price on valuation date	$ 3.00	$ 3.15	$ 2.97
Contractual exercise rate	$ 2.4648	$ 2.7500	$ 2.4648
Term (years)	6 months 15 days	1 year 6 months 15 days	1 year 3 months 11 days
Level 2 [Member] | Minimum [Member]
Derivative [Line Items]
Range of market volatilities	26.30%	38.70%	33.80%
Risk free rates using zero coupon US Treasury Security rates	0.02%	0.06%	0.02%
Level 2 [Member] | Maximum [Member]
Derivative [Line Items]
Range of market volatilities	46.10%	69.20%	63.60%
Risk free rates using zero coupon US Treasury Security rates	0.04%	0.20%	0.16%
Level 3 [Member]
Derivative [Line Items]
Linked common shares	1,562,500	1,562,500	1,562,500
Quoted market price on valuation date	$ 3.00	$ 3.15	$ 2.97
Contractual exercise rate	$ 3.60	$ 3.60	$ 3.60
Term (years)	3 years 7 months 10 days	4 years 7 months 6 days	4 years 4 months 6 days
Level 3 [Member] | Minimum [Member]
Derivative [Line Items]
Range of market volatilities	38.20%	54.20%	39.20%
Risk free rates using zero coupon US Treasury Security rates	0.02%	0.10%	0.05%
Level 3 [Member] | Maximum [Member]
Derivative [Line Items]
Range of market volatilities	60.50%	71.00%	70.20%
Risk free rates using zero coupon US Treasury Security rates	0.63%	0.47%	0.54%