Commitments (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 30, 2010	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating leases
Initial term of the operating lease for office and laboratory space	5 years
Extension term upon the completion of the initial lease term	5 years
Rent expense		$ 400	$ 200	$ 1,000	$ 700
Future minimum payments required under the non-cancellable operating lease
Remainder 2017		340		340
2018		1,379		1,379
2019		1,421		1,421
2020		721		721
Total minimum lease payments		$ 3,861		$ 3,861