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Derivative Instruments and Risk Management Activities - Notional Value of the Annual Expiration of Swaps in Effect (Details) $ in Millions | Dec. 31, 2018 USD ($)
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2019 |
Derivative [Line Items] |
Notional amount of swaps expiring | $ 353.0
2020 |
Derivative [Line Items] |
Notional amount of swaps expiring | 253.0
2021 |
Derivative [Line Items] |
Notional amount of swaps expiring | 111.3
2022 |
Derivative [Line Items] |
Notional amount of swaps expiring | 18.1
2023 |
Derivative [Line Items] |
Notional amount of swaps expiring | 13.6
2024 |
Derivative [Line Items] |
Notional amount of swaps expiring | $ 4.2

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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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