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v3.19.1

Accounting for Derivative Instruments and Hedging Activities - Net notional volume buy/sell of open derivative transactions (Details) shares in Millions, mw_per_day in Millions, bbl in Millions, T in Millions, MWh in Millions, MMBTU in Millions, $ in Millions | 3 Months Ended | 12 Months Ended
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Mar. 31, 2019 USD ($) MWh MMBTU mw_per_day T shares bbl | Dec. 31, 2018 USD ($) MWh MMBTU mw_per_day T shares bbl
Long | Emissions |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, nonmonetary notional amount, mass (ton) | 1 | 2
Long | Renewable Energy Certificates |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, non-monetary notional amount (in shares) | shares | 1 | 1
Long | Coal |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, nonmonetary notional amount, mass (ton) | 9 | 13
Long | Oil |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, nonmonetary notional amount (in barrels)) | bbl | 0 | 1
Long | Power |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, nonmonetary notional amount, energy (in MMBtu and MWh) | MWh | 8 | 1
Long | Interest |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, notional amount (in usd) | $ | $ 1,000 | $ 1,000
Short | Natural Gas |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, nonmonetary notional amount, energy (in MMBtu and MWh) | MMBTU | 236 | 330
Short | Capacity |  |
Volumetric Underlying Derivative Transactions |  |
Derivative, nonmonetary notional amount, flow rate (in MW/Day) | mw_per_day | (1) | (1)

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + 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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- Definition Derivative, Nonmonetary Notional Amount, Energy Flow Rate + References No definition available. + Details
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- Definition Derivative, Non-monetary Notional Amount, Other + References No definition available. + Details
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- Definition Volumetric Underlying Derivative Transactions [Abstract] + References No definition available. + Details
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- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Definition Nominal mass used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Definition Nominal volume used to calculate payments on a derivative instrument. + References No definition available. + Details
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