Description of the Business (Details) - USD ($)
$ / shares in Units, $ in Millions
Sep. 30, 2015
Apr. 02, 2014
Public Offering    
Common stock sold and issued (in shares)   8,626,377
Issuance price (in dollars per share) $ 34.00 $ 13.00
Net proceed from IPO. after deducting underwriting discounts and commissions and other offering expenses   $ 100.3
Net proceeds from sale of common stock net accrued costs $ 117.1  
Underwriting discounts and commissions 5.5 7.8
Offering expenses $ 0.6 $ 4.0
Redeemable convertible preferred stock converted into shares of common stock   23,501,208
Preferred stock warrant liability   $ 0.8
Public    
Public Offering    
Common stock sold and issued (in shares) 3,625,000  
Underwriters' over-allotment option    
Public Offering    
Common stock sold and issued (in shares) 525,000