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Stock-based Compensation - Narrative (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Feb. 17, 2016
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Dec. 31, 2015
Stock-based Compensation arrangements              
Stock based compensation expense   $ 7,800,000 $ 5,100,000 $ 26,200,000 $ 23,000,000    
Tax deficiency on share-based compensation         2,100,000    
Restricted Stock Units              
Stock-based Compensation arrangements              
Granted (in shares)       57,028      
Granted (in dollars per share)       $ 22.94      
Performance Share Awards | Minimum              
Stock-based Compensation arrangements              
Annual forfeiture rate assumption (as a percent)       0.00%      
Performance Share Awards | Maximum              
Stock-based Compensation arrangements              
Annual forfeiture rate assumption (as a percent)       6.00%      
Performance Share Awards Based on Internal Performance Metrics              
Stock-based Compensation arrangements              
Right to receive additional shares, maximum (as a percent)       100.00%      
Employee Performance Share Awards              
Stock-based Compensation arrangements              
Granted (in shares)       406,460      
Granted (in dollars per share)       $ 22.60      
Number of years over which performance criteria is to be met       3 years      
Hybrid Performance Share Awards              
Stock-based Compensation arrangements              
Granted (in shares)       272,920      
Granted (in dollars per share)       $ 22.60      
Minimum operating cash flow for the year preceding the performance period       $ 100,000,000      
Hybrid Performance Share Awards | Hybrid performance share awards, percentage vesting on the first anniversary              
Stock-based Compensation arrangements              
Award vesting rights (as a percent)   25.00%          
Hybrid Performance Share Awards | Hybrid performance share awards, percentage vesting on the second anniversary              
Stock-based Compensation arrangements              
Award vesting rights (as a percent)   25.00%          
Hybrid Performance Share Awards | Hybrid performance share awards, percentage vesting on the third anniversary              
Stock-based Compensation arrangements              
Award vesting rights (as a percent)   50.00%          
Performance Shares Based on Market Conditions              
Stock-based Compensation arrangements              
Right to receive shares (as a percent)       100.00%      
Right to receive an additional award in cash (as a percent)       100.00%      
TSR Performance Share Awards              
Stock-based Compensation arrangements              
Granted (in shares)       409,380      
Granted (in dollars per share) $ 19.85            
Performance period       3 years      
TSR Performance Share Awards | Minimum              
Stock-based Compensation arrangements              
Granted (in dollars per share)       $ 12.28      
TSR Performance Share Awards | Maximum              
Stock-based Compensation arrangements              
Granted (in dollars per share)       $ 20.22      
Accounting Standards Update 2017-07 | New Accounting Pronouncement, Early Adoption, Effect              
Stock-based Compensation arrangements              
Increase in deferred tax expense       $ 2,600,000 $ 1,200,000 $ 1,600,000 $ 1,400,000