Quarterly report pursuant to Section 13 or 15(d)

Employee Stock Plans - Summary of Restricted Stock Awards and Units (Details)

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Employee Stock Plans - Summary of Restricted Stock Awards and Units (Details) - $ / shares
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Sep. 30, 2016
Dec. 31, 2015
2010 Plan      
Stock-based compensation      
Maximum number of shares of common stock that may be issued 2,130,000 2,130,000  
Restricted Stock Share Awards      
Shares      
Unvested at the beginning of the period (in shares)   14,701  
Vested (in shares)   (14,701)  
Cancelled and forfeited (in shares)   0  
Unvested at the end of the period (in shares)     14,701
Weighted Average Grant Date Fair Value      
Unvested at the beginning of the period (in dollars per share)   $ 14.78  
Granted (in dollars per share)   0.00  
Vested (in dollars per share)   14.78  
Unvested at the end of the period (in dollars per share)     $ 14.78
Weighted Average Remaining Contractual Term      
Unvested at the beginning of the period     4 days
Unvested at the end of the period     4 days
Performance Share Unit Awards | 2010 Plan      
Weighted Average Grant Date Fair Value      
Granted (in dollars per share)   $ 19.88  
Restricted Stock Unit Awards      
Shares      
Unvested at the beginning of the period (in shares)   48,665  
Granted (in shares)   131,765  
Vested (in shares)   (131,638)  
Unvested at the end of the period (in shares) 48,792 48,792 48,665
Expected to vest in the future, at the end of the period (in shares) 47,035 47,035  
Weighted Average Grant Date Fair Value      
Unvested at the beginning of the period (in dollars per share)   $ 17.33  
Granted (in dollars per share)   21.37  
Vested (in dollars per share)   20.27  
Cancelled and forfeited (in dollars per share)   0.00  
Unvested at the end of the period (in dollars per share) $ 20.30 20.30 $ 17.33
Expected to vest in the future, at the end of the period (in dollars per share) $ 20.30 $ 20.30  
Weighted Average Remaining Contractual Term      
Unvested at the beginning of the period 1 year 2 months 27 days   1 year
Granted   5 months 5 days  
Unvested at the end of the period 1 year 2 months 27 days   1 year
Expected to vest in future, at the end of the period 1 year 2 months 27 days