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Stock-Based Compensation (Assumptions for PSU Awards) (Details) - Performance Shares [Member] - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 2.61% 1.59%
Expected life 2 years 8 months 12 days 3 years
Expected volatility 34.70% 36.50%
Expected dividends $ 0 $ 0
Forfeiture rate 0.00% 0.00%