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Schedule of Assumptions Used to Estimate the Fair Value of Stock Options Granted (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Risk-free interest rate, minimum 2.21% 1.43%
Risk-free interest rate, maximum 2.47% 2.40%
Expected term (in years) 10 years 10 years
Expected volatility, minimum 29.07% 24.03%
Expected volatility, maximum 34.43% 26.95%