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Description of Business (Details) - USD ($)
$ in Thousands
1 Months Ended 12 Months Ended
Mar. 12, 2018
Oct. 06, 2017
Nov. 29, 2016
Mar. 31, 2018
Aug. 02, 2017
Dec. 31, 2015
IPO            
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]            
Financing proceeds           $ 37,600
Follow-on Offering            
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]            
Financing proceeds           49,000
ATM Offering            
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]            
Financing proceeds         $ 19,300 $ 58,700
Maximum available under ATM offering $ 60,000   $ 40,000      
Number of shares of common stock sold       0 1,940,656  
Commissions paid         $ 398  
Other costs         $ 163  
Public Offering            
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]            
Financing proceeds   $ 55,200        
Number of shares issued   5,750,000        
Fees and commissions   $ 3,700