Income taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Components of (loss) income before provision for income taxes by jurisdiction
United States	$ (6,307,445)	$ (1,570,453)	$ (5,159,617)
Outside United States	2,002,251	4,287,085	2,098,049
(Loss) income from operations before provision for income taxes	(4,305,194)	2,716,632	(3,061,568)
Current tax:
United States-State and local	11,056	5,111	3,219
Outside United States	417,837	326,792
Total current tax	428,893	331,903	3,219
Deferred tax:
Outside United States	(281,782)
Total deferred tax	(281,782)
Provision for income taxes, net	147,111	331,903	3,219
Amount of deferred tax asset from which it is more likely than not that the Company would realize the benefit	29,238,264	26,452,590
Valuation allowance	29,200,000
Deferred tax benefit / net deferred tax asset	$ 182,892