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Share-Based Compensation - Narrative (Details)
$ / shares in Units, $ in Millions
9 Months Ended 12 Months Ended
Jan. 30, 2018
Jan. 16, 2018
USD ($)
$ / shares
Sep. 30, 2018
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
shares
Dec. 31, 2016
shares
Dec. 31, 2015
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Canceled or forfeited (in shares) | shares       8,963      
Stockholders' Equity Note, Stock Split, Conversion Ratio 1.5543            
Share based compensation options outstanding (in shares) | shares       1,515,461 1,644,212    
Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Allocated Share-based Compensation Expense       $ 8.5      
Unrecognized stock option compensation expense       $ 1.9      
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition       2 years 3 months      
Performance Shares [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based Compensation Arrangement by Share-based Payment Award, Consecutive Trading Day Period   60 days          
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period   181 days          
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost   $ 2.9          
Restricted Stock [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Canceled or forfeited (in shares) | shares         0 0 0
Allocated Share-based Compensation Expense       $ 2.4      
Unrecognized stock option compensation expense       $ 7.6      
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition       3 years 7 months      
Long-Term Incentive Plan [Member] | Performance Shares [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share based compensation options outstanding (in shares) | shares       700,000      
Tranche B [Member] | Long-Term Incentive Plan [Member] | Performance Shares [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Internal rate of return vesting threshold percentage   20.00%          
Return on investment threshold ratio   2.5          
Share-based Compensation Arrangement by Share-based Payment Award, Threshold Share Price | $ / shares   $ 19.11          
Tranche C [Member] | Long-Term Incentive Plan [Member] | Performance Shares [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Internal rate of return vesting threshold percentage   25.00%          
Return on investment threshold ratio   3.0          
Share-based Compensation Arrangement by Share-based Payment Award, Threshold Share Price | $ / shares   $ 22.93          
Maximum [Member] | Long-Term Incentive Plan [Member] | Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period     5 years        
Maximum [Member] | Tranche A [Member] | Long-Term Incentive Plan [Member] | Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Tranche vesting percentage       25.00%      
Minimum [Member] | Long-Term Incentive Plan [Member] | Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period       4 years      
Minimum [Member] | Tranche A [Member] | Long-Term Incentive Plan [Member] | Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Tranche vesting percentage       20.00%