Property and equipment (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Property and equipment
Property and equipment, gross	$ 4,083,154		$ 4,083,154		$ 2,947,464
Less: Accumulated depreciation and amortization	(1,958,204)		(1,958,204)		(1,551,310)
Property and equipment, net	2,124,950		2,124,950		1,396,154
Depreciation and amortization expense	136,193	123,970	407,684	395,573
Equipment
Property and equipment
Property and equipment, gross	938,143		938,143		923,356
Equipment | Minimum
Property and equipment
Estimated useful life			2 years
Equipment | Maximum
Property and equipment
Estimated useful life			5 years
Computer hardware
Property and equipment
Property and equipment, gross	2,287,264		2,287,264		1,688,262
Computer hardware | Minimum
Property and equipment
Estimated useful life			3 years
Computer hardware | Maximum
Property and equipment
Estimated useful life			5 years
Furniture and fixtures
Property and equipment
Property and equipment, gross	182,319		182,319		72,155
Furniture and fixtures | Minimum
Property and equipment
Estimated useful life			5 years
Furniture and fixtures | Maximum
Property and equipment
Estimated useful life			7 years
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 675,428		$ 675,428		$ 263,691
Leasehold improvements | Minimum
Property and equipment
Estimated useful life			5 years
Leasehold improvements | Maximum
Property and equipment
Estimated useful life			9 years