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Summary of Significant Accounting Policies - Share-based Compensation (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2015
Performance shares    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares awarded as a percentage of granted   200.00%
Performance Share Units with Total Shareholder Return Conditions    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 3 years  
Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Compensation cost recognition period 3 years  
Minimum | Performance shares    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares awarded as a percentage of granted 0.00%  
Vesting period 3 years  
Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Compensation cost recognition period 5 years  
Maximum | Performance shares    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares awarded as a percentage of granted 200.00%  
Vesting period 5 years