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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)
 12 Months Ended
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]  
Assumptions used in option pricing model and grant date fair value of options
We use the Black-Scholes option-pricing model to estimate the fair value of each option grant as follows: 
 
Weighted-average
 
2012
 
2013
 
2014
Grant-date fair value per option awarded
$
16.27

 
$
19.56

 
$
21.12

Assumptions used:
 
 
 
 
 
Expected life in years
6.8

 
7.0

 
7.0

Expected volatility
32
%
 
31
%
 
30
%
Dividend yield
2.1
%
 
2.1
%
 
2.2
%
Risk-free interest rate
1.3
%
 
1.9
%
 
2.2
%