Property and equipment (Tables)

12 Months Ended

Dec. 31, 2014

Property and equipment

Schedule of property and equipment, net

		As of December 31,
	Estimated useful life (in years)
		2014			2013
Equipment	2 - 7	$	945,116		$	939,129
Computer hardware	3 - 5		2,963,629			2,493,658
Furniture and fixtures	5 - 7		194,399			182,562
Leasehold improvements	3 - 10		749,275			689,648
Total property and equipment, gross			4,852,419			4,304,997
Less: Accumulated depreciation and amortization			(2,712,672	)		(2,106,357	)
Total property and equipment, net		$	2,139,747		$	2,198,640

Schedule of property and equipment depreciation and amortization expense

	Year ended December 31,
	2014		2013		2012
Depreciation and amortization expense	$	621,695	$	554,765	$	532,784