Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Summary of Restricted Stock Awards and Units (Details)

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Stock Based Compensation - Summary of Restricted Stock Awards and Units (Details) - $ / shares
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2017
Dec. 31, 2016
2010 Plan      
Stock-based compensation      
Maximum number of shares of common stock that may be issued 2,130,000 2,130,000  
Performance Share Unit Awards | 2010 Plan      
Weighted Average Grant Date Fair Value      
Granted (in dollars per share)   $ 33.60  
Restricted Stock Unit Awards      
Shares      
Unvested at the beginning of the period (in shares)   47,790  
Granted (in shares)   127,750  
Vested (in shares)   (127,531)  
Unvested at the end of the period (in shares) 48,009 48,009 47,790
Expected to vest in the future, at the end of the period (in shares) 48,009 48,009  
Weighted Average Grant Date Fair Value      
Unvested at the beginning of the period (in dollars per share)   $ 20.31  
Granted (in dollars per share)   24.15  
Vested (in dollars per share)   22.94  
Cancelled and forfeited (in dollars per share)   0.00  
Unvested at the end of the period (in dollars per share) $ 23.56 23.56 $ 20.31
Expected to vest in the future, at the end of the period (in dollars per share) $ 23.56 $ 23.56  
Weighted Average Remaining Contractual Term      
Unvested at the beginning of the period 1 year   11 months 16 days
Granted   4 months 2 days  
Unvested at the end of the period 1 year   11 months 16 days
Expected to vest in future, at the end of the period 1 year