XML 41 R25.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2017
Summary of Significant Accounting Policies  
Schedule of fair value of stock options estimated at the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions

 

 

 

 

 

 

 

 

 

 

 

 

    

2017

    

 

2016

    

 

2015

 

 

Risk free interest rate

 

1.7

%  

 

1.3

%  

 

1.4

%  

 

Expected life

 

4.6

years

 

4.6

years

 

4.6

years

 

Expected volatility

 

13.0

%  

 

15.0

%  

 

17.0

%  

 

Expected dividend yield

 

1.0

%  

 

1.0

%  

 

1.0

%