Segment information (Schedule of Geographic Information about Revenues) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	$ 31,868,046	$ 28,091,330	$ 81,848,511	$ 84,750,150
China (including Hong Kong) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	15,898,377	12,055,254	43,490,979	45,348,053
Asia, Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	4,814,794	1,986,907	8,279,740	5,314,537
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	6,975,938	8,958,775	18,782,316	22,576,122
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	3,830,007	5,048,498	10,846,247	11,357,548
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	106,759	315	106,759	30,198
Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	104,409	41,581	152,599	123,692
Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	$ 137,762		$ 189,871