v3.8.0.1
Stockholders' Equity (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 11, 2017
Sep. 30, 2015
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2015
Jan. 01, 2018
Jan. 01, 2017
Dec. 31, 2016
Stockholders' Equity                
Proceeds from issuance of common stock, net of offering costs       $ 189,463 $ 117,112      
Authorized shares of capital stock     205,000,000 205,000,000        
Authorized shares of common stock     200,000,000 200,000,000       200,000,000
Authorized shares of preferred stock     5,000,000 5,000,000       5,000,000
Shares of common stock reserved for future issuance                
Outstanding stock options     4,559,176 4,559,176        
Possible future issuance under 2014 Equity Incentive Plan     4,415,593 4,415,593        
Outstanding restricted stock units     1,413,423 1,413,423        
Available for future issuance under employee stock purchase plan     1,000,000 1,000,000        
Total shares of common stock reserved for future issuance     11,388,192 11,388,192        
Equity Incentive Plan 2014                
Shares of common stock reserved for future issuance                
Total shares of common stock reserved for future issuance     4,415,593 4,415,593   2,625,292 2,357,579  
Common Stock                
Stockholders' Equity                
Shares issued 4,047,500 3,625,000 4,047,500   3,625,000      
Proceeds from issuance of common stock, net of offering costs $ 189,500 $ 117,100            
Common Stock | Underwriters' over-allotment option                
Stockholders' Equity                
Shares issued 547,500 525,000