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18. INTANGIBLE ASSETS (Details 3)
 12 Months Ended
Dec. 31, 2020
Disclosure of detailed information about intangible assets [line items]  
Annual average amortization rate 4.05%
Hydroelectric generation [member]  
Disclosure of detailed information about intangible assets [line items]  
Annual average amortization rate 9.06%
Wind power generation [member]  
Disclosure of detailed information about intangible assets [line items]  
Annual average amortization rate 8.88%
Administration [member]  
Disclosure of detailed information about intangible assets [line items]  
Annual average amortization rate 15.74%
Distribution [member]  
Disclosure of detailed information about intangible assets [line items]  
Annual average amortization rate 3.90%
Gas [member]  
Disclosure of detailed information about intangible assets [line items]  
Annual average amortization rate 3.48%