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Financial instruments - Long-term Energy Derivative Contracts (Detail) - Cash flow hedge | Dec. 31, 2018 MWh $ / MWh
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PJM Western HUB |
Derivative [Line Items] |
Notional quantity (MW-hrs) | MWh | 871,391
Receive average prices (per MW-hr) | $ / MWh | 36.33
PJM NI HUB |
Derivative [Line Items] |
Notional quantity (MW-hrs) | MWh | 2,438,697
Receive average prices (per MW-hr) | $ / MWh | 29.06
ERCOT North HUB |
Derivative [Line Items] |
Notional quantity (MW-hrs) | MWh | 2,997,939
Receive average prices (per MW-hr) | $ / MWh | 36.46

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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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