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Nature of Business and Significant Accounting Policies (Details 5)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Stock Option Awards      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Risk-free interest rate 0.00% 1.80% 0.90%
Expected dividend yield 0.00% 1.60% 1.60%
Expected term   6 years 4 years 3 months
Expected volatility 0.00% 26.60% 25.60%
Performance-based restricted stock unit [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Expected dividend yield 1.20% 1.60% 1.60%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount for Postvesting Restrictions 0.00% 0.00% 9.90%
Market-based restricted stock unit      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Risk-free interest rate 0.00% 0.00% 0.90%
Expected dividend yield 0.00% 0.00% 1.60%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount for Postvesting Restrictions 0.00% 0.00% 9.90%
Expected term     4 years
Expected volatility 0.00% 0.00% 25.80%
Expected volatility of S&P 500 0.00% 0.00% 25.00%
Employee Stock Purchase Plan (ESPP)      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Risk-free interest rate 2.30% 1.00% 0.50%
Expected dividend yield 1.30% 1.60% 1.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount for Postvesting Restrictions 10.50% 10.50% 10.50%
Expected term 6 months 6 months 6 months
Expected volatility 26.40% 20.90% 27.00%