v3.19.3.a.u2
Share-Based Payments - Total Shareholder Return Units Activity (Details) - Total Shareholder Return Units (TSRUs) [Member] - $ / shares
shares in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Nonvested, beginning of period, shares 138,945    
Granted, shares 39,246    
Vested, shares (47,710)    
Forfeited, shares (7,826)    
Nonvested, end of period, shares 122,654 138,945  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Nonvested, beginning of period, weighted-average grant date fair value per share (in dollars per share) $ 6.48    
Granted, weighted-average grant-date fair value per share (in dollars per share) 8.52 $ 7.42 $ 6.23
Vested, weighted-average grant date fair value per share (in dollars per share) 5.92    
Forfeited, weighted-average grant date fair value per share (in dollars per share) 7.63    
Nonvested, end of period, weighted-average grant date fair value per share (in dollars per share) 7.53 6.48  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Grant Price [Abstract]      
Outstanding, beginning of period, weighted-average exercise price per share (in dollars per share) 33.44    
Granted, weighted-average exercise price per share (in dollars per share) 43.35    
Forfeited, weighted-average exercise price per share (in dollars per share) 30.70    
Expired, weighted-average exercise price per share (in dollars per share) 38.90    
Outstanding, end of period, weighted-average exercise price per share (in dollars per share) $ 38.01 $ 33.44