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Stock-based Compensation - Restricted Stock Units Activity (Details) - Restricted Stock Units (RSUs) [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]      
Non-vested, beginning balance, shares 247 1,165 2,316
Granted, shares 439 135 214
Vested, shares (110) (1,034) (1,316)
Forfeited, shares (30) (19) (49)
Non-vested, ending balance, shares 546 247 1,165
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Non-vested, weighted average grant date fair value, beginning balance (in dollars per share) $ 34.22 $ 15.34 $ 11.23
Granted, weighted average grant date fair value (in dollars per share) 26.89 48.35 36.68
Vested, weighted average grant date fair value (in dollars per share) 24.98 14.86 11.46
Forfeited, weighted average grant date fair value (in dollars per share) 33.90 30.94 14.27
Non-vested, weighted average grant date fair value, ending balance (in dollars per share) $ 29.95 $ 34.22 $ 15.34