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Share-based Compensation (Valuation Assumptions) (Details)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2018
USD ($)
plan
$ / shares
Dec. 31, 2017
USD ($)
$ / shares
Dec. 31, 2016
USD ($)
$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Plans | plan 2    
Share-based Compensation, Fair Value Assumptions [Abstract]      
Weighted average fair values of stock options granted (in dollars per share) | $ / shares $ 11.80 $ 15.38 $ 19.50
Expected volatility 35.70% 37.90% 55.50%
Expected dividends 0.70% 0.56% 0.61%
Weighted average risk-free interest rate 2.47% 1.64% 1.40%
Expected life of stock options (in years) 3 years 6 months 3 years 6 months 3 years 6 months
Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock compensation expense | $ $ 449 $ 433 $ 340