Commitments and contingencies (Details) (USD $)	1 Months Ended	6 Months Ended	1 Months Ended
	Feb. 28, 2014	Jun. 30, 2014	May 31, 2014 Third amendment to the operating lease agreement for laboratory facility in Plymouth, Michigan sqft item
Commitments and contingencies
Term period of lease	63 months
Operating lease period for monthly rent increasing in fixed monthly rent		12 months
Operating lease period after which monthly rent increase		3 months
Commitments and contingencies
Adjusted rentable laboratory space (in square feet)			3,045
Adjusted proportionate share of landlord's expenses and taxes (as a percent)			7.40%
Number of terms which Company may exercise to renew lease			1
Lease renewal term			3 years
Annual base rent under new lease agreement			$ 37,000
Operating leases
Total		615,000
Less than 1 Year		128,000
1-3 Years		267,000
3-5 Years		211,000
More than 5 Years		9,000
Total
Total		615,000
Less than 1 Year		128,000
1-3 Years		267,000
3-5 Years		211,000
More than 5 Years		$ 9,000