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Share Based Payments (Details 3)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Weighted average expected stock-price volatility 28.00% 29.00%
Weighted average expected option life 5 years 5 years
Weighted average risk-free interest rate 2.50% 2.00%
Weighted average dividend yield 2.00% 2.10%