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Stock-Based Compensation - Nonvested Restricted Stock Unit Activity (Details) - Nonvested Restricted Stock Units
12 Months Ended
Dec. 31, 2017
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Nonvested beginning balance (in Shares) 1,066,207
Granted (in Shares) 129,569
Vested (in Shares) (296,608)
Forfeited (in Shares) (47,271)
Nonvested ending balance (in Shares) 851,897
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]  
Nonvested, weighted-average grant date fair value, beginning balance (in Dollars per share) | $ / shares $ 32.21
Vested, weighted-average grant date fair value (in Dollars per share) | $ / shares 30.03
Forfeited, weighted-average grant date fair value (in Dollars per share) | $ / shares 47.49
Nonvested, weighted-average grant date fair value, ending balance (in Dollars per share) | $ / shares $ 40.61