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REGULATORY MATTERS (Rate Order) (Details) (USD $)
 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Jun. 30, 2013
TUCSON ELECTRIC POWER COMPANY
Dec. 31, 2013
TUCSON ELECTRIC POWER COMPANY
Dec. 31, 2012
TUCSON ELECTRIC POWER COMPANY
Dec. 31, 2011
TUCSON ELECTRIC POWER COMPANY
Dec. 31, 2013
UNS Electric
Jun. 30, 2013
UNS Gas
Apr. 30, 2012
UNS Gas
Jun. 30, 2013
Before July 1, 2013 [Member]
TUCSON ELECTRIC POWER COMPANY
Jun. 30, 2013
After June 30, 2013 [Member] [Member]
TUCSON ELECTRIC POWER COMPANY
Schedule of Regulatory Orders [Line Items]                        
Base rate increase approved       $ 76,000,000       $ 3,000,000   $ 2,700,000    
Original cost rate base       1,500,000,000       213,000,000   183,000,000    
Fair value of rate base       2,300,000,000       283,000,000        
Approved rate of return on equity       10.00%       9.50%        
Approved long term cost of debt       5.18%       5.97%        
Approved short-term cost of debt       1.42%                
Approved weighted average cost of capital       7.26%       7.83%        
Approved equity portion of capital structure       43.50%       52.60%        
Approved long term debt portion of capital structure       56.00%       47.40%        
Approved short-term debt portion of capital structure       0.50%                
Approved rate of return on the fair value increment of rate base       0.68%       0.50%   1.00%    
Fair value increment of rate base       800,000,000       70,000,000   70,000,000    
Change in composite rate                     3.32% 3.00%
Expected change in annual depreciation       11,000,000                
PPFAC credit       0.1388                
PPFAC Reduction - TEP Rate Order 3,000,000 0 0 3,000,000 3,000,000 0 0          
Deferred costs related to San Juan Mine Fire       10,000,000                
Revenue Recognized Under Lost Fixed Cost Recovery Mechanism       2,000,000                
Environmental compliance adjustor capped rate       0.025                
Retail revenue cap on environmental compliance adjustor       0.25%                
Approved energy efficiency budget       21,000,000       5,000,000 2,000,000      
Performance Incentive Included in Efficiency Budget       $ 2,000,000                
Percentage increase in base rates approved by regulator                   1.80%    
Authorized rate of return                   8.30%