Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Activity (Details)

v3.5.0.2
Share-Based Compensation - Activity (Details) - USD ($)
9 Months Ended
Feb. 22, 2016
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Unrecognized share-based compensation expense        
Restricted stock awards, Unrecognized compensation expense   $ 13,703,000    
Stock options, Unrecognized compensation expense   5,447,000    
Total unrecognized compensation expense related to unvested awards   $ 19,150,000    
Restricted Stock Awards        
Restricted Stock Awards, Number of Shares        
Balance at beginning of period (in shares)   586,600    
Granted (in shares)   340,900    
Converted/Exercised (in shares)   (205,800)    
Forfeited (in shares)   (32,900)    
Balance at end of period (in shares)   688,800    
Restricted Stock Awards, Weighted Average Grant Date Fair Value Per Share        
Balance at beginning of period (in dollars per share)   $ 21.97    
Granted (in dollars per share)   28.99    
Converted/Exercised (in dollars per share)   21.17    
Forfeited (in dollars per share)   25.45    
Balance at end of period (in dollars per share)   $ 25.51    
Unrecognized share-based compensation expense        
Restricted stock awards, Weighted average remaining vesting period   1 year 9 months 18 days    
Assumptions used to estimate the fair values of the awards granted:        
Remaining measurement period   2 years 10 months 10 days    
Risk free interest rate (as a percent)   0.90%    
Dividend yield (as a percent)   0.00%    
Estimated fair value of awards granted (in dollars per share)   $ 33.77    
Stock Options        
Stock Options, Number of Shares        
Balance at beginning of period (in shares)   387,600    
Granted (in shares)   409,300    
Exercised (in shares)   (3,700)    
Forfeited (in shares)   (34,900)    
Balance at end of period (in shares)   758,300    
Stock Options, Weighted Average Grant Date Fair Value Per Share        
Balance at beginning of period (in dollars per share)   $ 9.35    
Granted (in dollars per share)   10.20    
Converted/Exercised (in dollars per share)   10.35    
Forfeited (in dollars per share)   10.28    
Balance at end of period (in dollars per share)   9.76    
Stock Options, Weighted Average Exercise Price Per Share        
Balance at beginning of period (in dollars per share)   24.03    
Granted (in dollars per share)   26.30    
Exercised (in dollars per share)   26.81    
Forfeited (in dollars per share)   26.58    
Balance at end of period (in dollars per share)   $ 25.13    
Stock options, additional disclosures        
Aggregate intrinsic value   $ 6,122,500   $ 2,611,700
Converted/Exercised aggregate intrinsic value   $ 37,300    
Exercisable, Number of shares   113,900    
Exercisable, Weighted Average Grant Date Fair Value Per Share   $ 8.08    
Exercisable Weighted Average Exercise Price Per Share   $ 20.65    
Exercisable, Aggregate Intrinsic Value   $ 1,429,200    
Weighted average remaining contractual term for vested but unexercised stock options   6 years 9 months 18 days    
Unrecognized share-based compensation expense        
Stock options, Weighted average remaining vesting period   1 year 10 months 24 days    
Assumptions used to estimate the fair values of the awards granted:        
Risk free interest rate (as a percent)   1.51% 1.82%  
Expected volatility using historical return volatility and implied volatility (as a percent)   38.00% 37.00%  
Expected life (in years)   6 years 6 years  
Dividend yield (as a percent)   0.00% 0.00%  
Estimated fair value of awards granted (in dollars per share)   $ 10.20 $ 10.44  
Performance-based conditions | Restricted Stock Awards        
Restricted stock awards, additional disclosures        
Grant date fair value $ 2,251,000      
Performance-based conditions | Restricted Stock Awards | Payout Range-25%        
Restricted stock awards, additional disclosures        
Related expenses 563,000      
Performance-based conditions | Restricted Stock Awards | Payout Range-100%        
Restricted stock awards, additional disclosures        
Related expenses 2,251,000      
Performance-based conditions | Restricted Stock Awards | Payout Range-200%        
Restricted stock awards, additional disclosures        
Related expenses $ 4,502,000