Long-term loans (Details)			3 Months Ended		6 Months Ended
	Jun. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Jun. 30, 2013 Bank Of China [Member] USD ($)	Jun. 30, 2012 Bank Of China [Member] USD ($)	Jun. 30, 2013 Bank Of China [Member] USD ($)	Jun. 30, 2012 Bank Of China [Member] USD ($)	Jun. 30, 2013 Bank Of China [Member] CNY	Dec. 31, 2012 Bank Of China [Member] USD ($)
Debt Instrument [Line Items]
Long term loan term					5 years
Long-term loans, face amount			$ 7,954,437		$ 7,954,437		50,000,000
Long term loans from Bank of China			6,795,567		6,795,567			7,703,048
Less: current portion of long-term borrowings	1,941,590	1,925,762	1,941,590		1,941,590			1,925,762
Long-term borrowings, net of current portion	4,853,977	5,777,286	4,853,977		4,853,977			5,777,286
Interest rate multiple			110.00%		110.00%
Maximum interest rate					7.04%
Interest on long-term loans			130,939	165,732	282,224	185,705
Percent of principle to be paid in prior year					2.00%
Percent of principle to be paid in subsequent periods					6.00%
Repayment schedule of the principal
Remaining 2013			970,797		970,797
2014			1,941,590		1,941,590
2015			1,941,590		1,941,590
2016			$ 1,941,590		$ 1,941,590