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Stock-Based Compensation (Narrative) (Details)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2016
USD ($)
employee
$ / shares
shares
Dec. 31, 2015
USD ($)
$ / shares
shares
Dec. 31, 2014
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Annual vesting percentage 25.00%    
Vesting period 3 years    
Expiration period 10 years    
Capitalized Amount $ 500 $ 600 $ 400
Allocated stock-based compensation expense $ 12,286 $ 9,255 $ 7,867
Number of options vested and expected to vest (in shares) | shares 11,500 31,500 31,500
Termination      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 90 days    
Death, Disability, or Retirement      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 365 days    
Employee Stock Option      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 10 years    
Aggregate Intrinsic Value $ 2,656 $ 3,164 $ 2,600 [1]
Allocated stock-based compensation expense 7,400 $ 5,300 $ 4,300
Unrecognized compensation expense related to granted but unvested stock options $ 14,300    
Unrecognized compensation cost, period for recognition 2 years 9 months 18 days    
Number of options vested and expected to vest (in shares) | shares 7,906,267    
Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation expense related to granted but unvested stock options $ 5,200    
Unrecognized compensation cost, period for recognition 2 years 1 month 6 days    
Weighted average grant date fair value of shares granted (in USD per share) | $ / shares $ 8.29 $ 16.03 $ 13.25
Fair value of shares vested $ 2,600 $ 2,200 $ 7,600
Restricted stock expense $ 3,700 $ 2,800 $ 2,600
Stock units granted (in shares) | shares [2] 758,128    
Shares of unvested restricted stock (in shares) | shares [2] 1,310,019 885,060  
Performance stock units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock units granted (in shares) | shares [2] 233,482    
2015 Stock Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock, shares authorized (shares) | shares 6,786,760    
Shares available for grant under the plan (in shares) | shares 2,700,000    
2015 Stock Incentive Plan | Employee Stock Option      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Estimated forfeiture rate 11.00% 14.00% 14.00%
2015 Stock Incentive Plan | Employee Stock Option | Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Option exercise price as a percentage of grant date fair value 100.00%    
Employee Stock Purchase Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares available for grant under the plan (in shares) | shares 1,400,000    
Discount from market price 15.00%    
Unrecognized compensation expense related to granted but unvested stock options $ 1,205 $ 921 $ 841
Non-Employee Restricted Stock | Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated stock-based compensation expense $ 30 $ 100 $ 100
Stock units granted (in shares) | shares 0    
Shares of unvested restricted stock (in shares) | shares 41,000 72,000 10,000
Award Modifications | Performance stock units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated stock-based compensation expense $ 273 $ 46 $ 85
Number of employees affected by award modification | employee 4    
Award Modifications | Performance stock units | Minimum | Employee One      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 90 days    
Award Modifications | Performance stock units | Minimum | Employee Two      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 90 days    
Award Modifications | Performance stock units | Minimum | Employee Three      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 90 days    
Award Modifications | Performance stock units | Maximum | Employee One      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 150 days    
Award Modifications | Performance stock units | Maximum | Employee Two      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 180 days    
Award Modifications | Performance stock units | Maximum | Employee Three      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 180 days    
[1] Represents the total difference between the Company's stock price at the time of exercise and the stock option exercise price, multiplied by the number of options exercised.
[2] Shares granted in 2016 include 233,482 performance stock units that have certain performance conditions required to be achieved to vest.