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Stock-Based Compensation Restricted Stock Units Activity (Details)
3 Months Ended
Mar. 31, 2018
$ / shares
shares
RSU  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Outstanding, shares, beginning of period (shares) | shares 1,104,792
Granted (shares) | shares 431,775
Vested (shares) | shares (337,275)
Forfeited (shares) | shares (5,715)
Outstanding and nonvested, shares, end of period (shares) | shares 1,184,076
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]  
Outstanding, weighted average fair value, beginning of period (usd per share) | $ / shares $ 32.62
Granted, weighted average fair value (usd per share) | $ / shares 41.92
Vested, weighted average fair value (usd per share) | $ / shares 34.76
Forfeited, weighted average fair value (usd per share) | $ / shares 30.57
Outstanding and nonvested, weighted average fair value, end of period (usd per share) | $ / shares $ 35.40
RSU Dividend Equivalent Unit (DEU)  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Granted (shares) | shares 7,257
Vested (shares) | shares (16,553)
Forfeited (shares) | shares (205)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]  
Granted, weighted average fair value (usd per share) | $ / shares $ 40.70
Vested, weighted average fair value (usd per share) | $ / shares 35.99
Forfeited, weighted average fair value (usd per share) | $ / shares $ 37.39