Property and Equipment (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Components of property and equipment
Property and equipment, gross	$ 81,239,315	$ 78,079,102
Less: accumulated depreciation	(20,315,999)	(18,643,002)
Property and equipment, net	60,923,316	59,436,100
Office equipment and furniture [Member]
Components of property and equipment
Property and equipment, useful life	5 years
Property and equipment, gross	225,233	222,853
Manufacturing equipment [Member]
Components of property and equipment
Property and equipment, gross	59,938,834	56,916,700
Manufacturing equipment [Member] | Minimum [Member]
Components of property and equipment
Property and equipment, useful life	5 years
Manufacturing equipment [Member] | Maximum [Member]
Components of property and equipment
Property and equipment, useful life	10 years
Vehicles [Member]
Components of property and equipment
Property and equipment, useful life	5 years
Property and equipment, gross	125,854	125,167
Construction in progress [Member]
Components of property and equipment
Property and equipment, useful life	0 years
Property and equipment, gross	49,638	28,785
Building and building improvements [Member]
Components of property and equipment
Property and equipment, useful life	20 years
Property and equipment, gross	$ 20,899,756	$ 20,785,597