Income taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components of income (loss) before provision for income taxes by jurisdiction
United States	$ 537,097	$ (6,307,445)	$ (1,570,453)
Outside United States	(474,222)	2,002,251	4,287,085
Income (loss) from operations before provision for income taxes	62,875	(4,305,194)	2,716,632
Current tax:
United States-State and local	5,754	11,056	5,111
Outside United States	619,043	417,837	326,792
Total current tax	624,797	428,893	331,903
Deferred tax:
Outside United States	(583,928)	(281,782)
Total deferred tax	(583,928)	(281,782)
Provision for income taxes, net	40,869	147,111	331,903
Amount of deferred tax asset from which it is more likely than not that the Company would realize the benefit	31,200,000	29,200,000
Valuation allowance	29,416,464	29,238,264
Deferred tax liability	1,000,000
Deferred tax liability/ net deferred tax asset	$ 766,242	$ 182,892	$ 0