Segment information (Schedule of Geographic Information about Accounts Receivable) (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	$ 23,961,421	$ 21,129,418
Hong Kong and China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	14,392,770	14,359,354
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	1,465,103	740,289
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	6,848,643	4,973,601
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	1,215,445	1,036,100
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	16,615	18,950
Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	19,140	1,124
Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Accounts receivable	$ 3,705