XML 146 R118.htm IDEA: XBRL DOCUMENT
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Financial Instruments (Details) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2018 USD ($) | Dec. 31, 2017 CAD ($) MW | Dec. 31, 2017 USD ($) | Dec. 31, 2018 CAD ($) MW | Dec. 31, 2018 USD ($) MW | Dec. 31, 2017 USD ($) MW | Dec. 31, 2016 CAD ($)
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Risk management assets (Note 14 and 15) |  | $ 219,000,000 |  | $ 146,000,000 |  |  |
Increase (decrease) in derivative forward power prices, reasonable possible | $ 6 |  | $ 6 |  |  |  |
Decrease in base fair value |  | 62,000,000 |  |  |  |  |
Decrease in sensitivity values |  | $ 9,000,000 |  |  |  |  |
Fixed-price contracts | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Long-term fixed price power sale contract, delivery volume | MW |  | 300 |  |  |  | 300 |
Fixed-price contracts | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Long-term fixed price power sale contract, delivery volume | MW |  |  |  | 380 | 380 |  |
Unit Contingent Power Purchases | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Volume discount ranges, percent | 2.20% | 2.20% | 2.20% |  |  |  |
Sensitivity analysis in derivative, price discount, percent | 1.10% | 1.10% | 1.10% |  |  |  |
Sensitivity analysis in derivative, volume discount ranges, percent | 8.60% | 7.80% | 7.80% |  |  |  |
Unit Contingent Power Purchases | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Volume discount ranges, percent | 16.90% | 2.76% | 2.76% |  |  |  |
Sensitivity analysis in derivative, price discount, percent | 1.90% | 1.90% | 1.90% |  |  |  |
Sensitivity analysis in derivative, volume discount ranges, percent | 27.30% | 10.50% | 10.50% |  |  |  |
Structured Products - Eastern U.S. |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Sensitivity analysis in derivative, basis relationship, percent |  | 7.00% | 7.00% |  |  |  |
Sensitivity analysis in derivative, non-standard shape factors, percent |  | 6.00% | 6.00% |  |  |  |
Sensitivity Analysis In Derivative, Implied Correlations, Percent | 3000.00% |  |  |  |  |  |
Sensitivity Analysis In Derivative, Implied Volatility And Correlation, Percent |  | 1000.00% | 1000.00% |  |  |  |
Structured Products - Eastern U.S. | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Basis relationship, percent | 75.00% | 75.00% | 75.00% |  |  |  |
Non-standard shape factors, percent | 63.00% | 71.00% | 71.00% |  |  |  |
Sensitivity analysis in derivative, basis relationship, percent | 4.20% |  |  |  |  |  |
Sensitivity analysis in derivative, non-standard shape factors, percent | 4.00% |  |  |  |  |  |
Implied volatility for shares, significant unobservable inputs, entity's own derivative | 25.00% | 18.00% | 18.00% |  |  |  |
Implied correlations for shares, significant unobservable inputs, entity's own derivative | 70.00% | 70.00% | 70.00% |  |  |  |
Sensitivity Analysis In Derivative, Implied Volatility, Percent | 37.00% | 2700.00% | 2700.00% |  |  |  |
Structured Products - Eastern U.S. | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Basis relationship, percent | 109.00% | 159.00% | 159.00% |  |  |  |
Non-standard shape factors, percent | 104.00% | 88.00% | 88.00% |  |  |  |
Sensitivity analysis in derivative, basis relationship, percent | 6.90% |  |  |  |  |  |
Sensitivity analysis in derivative, non-standard shape factors, percent | 9.30% |  |  |  |  |  |
Implied volatility for shares, significant unobservable inputs, entity's own derivative | 84.00% | 54.00% | 54.00% |  |  |  |
Sensitivity Analysis In Derivative, Implied Volatility, Percent | 49.00% | 3200.00% | 3200.00% |  |  |  |
Long-Term Wind Energy Sale - Eastern U.S. |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Sensitivity Analysis In Derivative, Implied Correlations, Percent | 10.00% |  |  |  |  |  |
Long-term contracts | Long-Term Power Sale - Alberta |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Long-term fixed price power sale contract, delivery volume | MW |  |  |  | 12.5 | 12.5 |  |
Long-term contracts | UNITED STATES | Fixed-price contracts | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | $ 20 | $ 25 |
Long-term contracts | UNITED STATES | Fixed-price contracts | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | 35 | $ 34 |
Long-term contracts | Canada | Fixed-price contracts |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  | $ 40 |  |  |
Sensitivity analysis in derivative, forward price, percent | 20.00% |  |  |  |  |  |
Long-term contracts | Canada | Fixed-price contracts | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  | $ 63 |  |  |  |  |
Long-term contracts | Canada | Fixed-price contracts | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  | 67 |  |  |  |  |
Level III | Long-term contracts | Fixed-price contracts |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | 1 |  |
Level III | Long-term contracts | Fixed-price contracts | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | 7 |  |
Level III | Long-term contracts | Fixed-price contracts | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | 8 |  |
Level III | Long-term contracts | Forward contract |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | 6 |  |
Level III | Long-term contracts | Forward contract | Minimum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | 42 |  |
Level III | Long-term contracts | Forward contract | Maximum |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Forward power price ranges per MWh |  |  |  |  | $ 68 |  |
Recurring fair value measurement | Level I |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Risk exposure associated with instruments sharing characteristic |  | (1,000,000) |  | 3,000,000 |  |  |
Recurring fair value measurement | Level III |  |  |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |  |  |
Risk exposure associated with instruments sharing characteristic |  | $ 771,000,000 |  | $ 695,000,000 |  |  | $ 758,000,000

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