Goodwill and intangible assets - Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill, gross, at the Beginning of the period	$ 286,852	$ 319,671
Impact of change in Euro exchange rate	(10,066)	(32,819)
Goodwill, net, at the end of the period	$ 276,786	$ 286,852