Property and equipment (Tables)

12 Months Ended

Dec. 31, 2013

Property and equipment

Schedule of property and equipment, net

			As of December 31,
	Estimated useful life (in years)
			2013			2012
Equipment		2 - 5	$	939,129		$	923,356
Computer hardware		3 - 5		2,493,658			1,688,262
Furniture and fixtures		5 - 7		182,562			72,155
Leasehold improvements		5 - 9		689,648			263,691
Total property and equipment, gross				4,304,997			2,947,464
Less: Accumulated depreciation and amortization				(2,106,357	)		(1,551,310	)
Total property and equipment, net			$	2,198,640		$	1,396,154

Schedule of property and equipment depreciation and amortization expense

	Year ended December 31,
	2013		2012		2011
Depreciation and amortization expense	$	554,765	$	532,784	$	656,837