XML 102 R74.htm IDEA: XBRL DOCUMENT v3.8.0.1
Significant Accounting Policies (Details)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Coal generation | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   2 years
Coal generation | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   14 years
Gas generation | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   2 years
Gas generation | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   30 years
Hydro | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   3 years
Hydro | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   60 years
Wind Generation | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   3 years
Wind Generation | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   30 years
Mining property and equipment | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   2 years
Mining property and equipment | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   14 years
Capital spares and other | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   2 years
Capital spares and other | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life   30 years
Facilities | Minimum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life 30 years  
Facilities | Maximum    
Disclosure of detailed information about property, plant and equipment [line items]    
PP&E useful life 60 years  
Computer software | Minimum    
Disclosure of detailed information about intangible assets [line items]    
Intangible assets, useful life   2 years
Computer software | Maximum    
Disclosure of detailed information about intangible assets [line items]    
Intangible assets, useful life   7 years
Power sale contracts | Minimum    
Disclosure of detailed information about intangible assets [line items]    
Intangible assets, useful life   5 years
Power sale contracts | Maximum    
Disclosure of detailed information about intangible assets [line items]    
Intangible assets, useful life   20 years