Goodwill and intangible assets (Tables)

12 Months Ended

Dec. 31, 2014

Goodwill and intangible assets

Schedule of changes in carrying amount of goodwill

Goodwill, gross, as of December 31, 2012	$	347,599
Impact of change in Euro exchange rate		14,464
Accumulated impairment losses as of December 31, 2013		—
Goodwill, net, as of December 31, 2013		362,063
Impact of change in Euro exchange rate		(42,392	)
Accumulated impairment losses as of December 31, 2014		—
Goodwill, net, as of December 31, 2014	$	319,671

Schedule of the gross book value, accumulated amortization and amortization periods of intangible assets

	As of December 31, 2014							As of December 31, 2013
	Gross book value		Accumulated amortization			Net book value		Gross book value		Accumulated amortization			Net book value		Amortization period (in years)
Trademarks and patents	$	1,158,572	$	(387,134	)	$	771,438	$	1,100,696	$	(327,200	)	$	773,496		15 - 21
Technology		2,662,164		(1,386,902	)		1,275,262		3,015,192		(967,779	)		2,047,413		5
Intangible assets, net	$	3,820,736	$	(1,774,036	)	$	2,046,700	$	4,115,888	$	(1,294,979	)	$	2,820,909

Schedule of amortization expense related to intangible assets

	Year ended December 31,
	2014		2013		2012
Amortization expense	$	707,657	$	735,265	$	569,721

Schedule of intangible amortization expense that will be charged to income and is estimated on the basis of book value

Intangible amortization expense that will be charged to income for the subsequent five years and thereafter is estimated on the December 31, 2014 book value, as follows:

2015	$	616,552
2016		607,929
2017		285,893
2018		77,290
2019		72,439
Thereafter		386,597
Total	$	2,046,700