Warrants Issued and Outstanding (Detail) (Warrants, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Warrants
Warrants Outstanding Number of underlying shares
Beginning Balance	408,956	1,138,420	2,102,100
Granted/Vested	0	0	0
Forfeited	0	0	0
Exercised	(125,000)	(729,464)	(963,680)
Ending Balance	283,956	408,956	1,138,420	2,102,100
Warrants Outstanding Weighted Average Exercise Price
Beginning Balance	$ 3.59	$ 3.62	$ 3.59
Exercised	$ 3.50	$ 3.63	$ 3.55
Ending Balance	$ 3.63	$ 3.59	$ 3.62	$ 3.59
Warrants Outstanding Average Remaining Contractual Life (yrs)
Beginning Balance	10 months 28 days	1 year 10 months 20 days	2 years 10 months 28 days	3 years 11 months 5 days
Warrants Exercisable Number of underlying shares
Beginning Balance	408,956	1,138,420	1,964,100
Ending Balance	283,956	408,956	1,138,420	1,964,100
Warrants Exercisable Weighted Average Exercise Price
Beginning Balance	$ 3.59	$ 3.62	$ 3.50
Ending Balance	$ 3.63	$ 3.59	$ 3.62	$ 3.50
Warrants Exercisable Average Remaining Contractual Life (yrs)
Beginning Balance	10 months 28 days	1 year 10 months 20 days	2 years 10 months 28 days	3 years 8 months 27 days