Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Feb. 29, 2016	Dec. 31, 2016
Liquidity
Accumulated deficit	$ (305,850)			$ (185,526)
Initial Public Offering
Liquidity
Number of common stock issued	2,265,500	4,600,000	6,785,000
Price to the public			$ 16.00
Aggregate net proceeds			$ 97,500
Follow-on Offering
Liquidity
Number of common stock issued	295,500	4,600,000
Price to the public		$ 22.50
Aggregate net proceeds		$ 96,700
Public Offering
Liquidity
Number of common stock issued	2,265,500
Price to the public	$ 26.00
Aggregate net proceeds	$ 57,200
Overallotment Option
Liquidity
Number of common stock issued		600,000	885,000