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Stock-Based Compensation Plans - Additional Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Stock options granted (in shares) 228,438    
Restricted stock units award (in shares) 1,086,250    
Stock-based compensation expense $ 24,068 $ 11,390 $ 11,400
Total unrecognized compensation cost $ 56,000    
Unrecognized compensation cost reorganization period 2 years 10 months 20 days    
Outstanding Options at end of the period (in shares) 1,960,459    
2015 Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Shares Available for Grant, Equity Incentive Plans Shares Approved (in shares) 2,500,000    
2012 Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Shares Available for Grant, Equity Incentive Plans Shares Approved (in shares) 1,500,000    
Stock Options [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Stock options granted (in shares) 228,438 0 200,000
Outstanding Options at end of the period (in shares) 1,960,459 [1] 2,376,500  
Share based payment award expiration period 10 years    
Number of options that can be exercised within six months grant date (in shares) 0    
Aggregate intrinsic value of options exercised $ 34,100 $ 2,300 $ 22,800
Aggregate fair value of options vested $ 17,600 $ 9,000 $ 8,000
Stock Options [Member] | Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based payment award vesting period 4 years    
Cancellation period for unexercised vested options 30 days    
Stock Options [Member] | Maximum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based payment award vesting period 5 years    
Cancellation period for unexercised vested options 180 days    
Restricted stock units [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Restricted stock units award (in shares) 1,086,250 33,750 210,000
Restricted stock units unvested 1,140,125 [1] 188,000  
Restricted stock units [Member] | Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based payment award vesting period 2 years    
Restricted stock units [Member] | Maximum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based payment award vesting period 4 years    
[1] Includes 1,454,938 shares and 56,875 shares available for future grants under the 2015 Plan and the 2012 Plan, respectively. Additionally, 7,987 shares associated with the merger replacement stock options were unused.