v3.20.1

Accounting for derivative instruments and hedging activities - forecasted transactions (Details) kJ in Millions, MMBTU in Millions, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 USD ($) kJ MMBTU | Dec. 31, 2019 USD ($) kJ MMBTU
Natural gas swaps |  |
Derivative instruments |  |
Volume of forecasted transactions, energy (swaps: Mmbtu, agreements: joules) | MMBTU | 15.4 | 16.3
Gas purchase agreements |  |
Derivative instruments |  |
Volume of forecasted transactions, energy (swaps: Mmbtu, agreements: joules) | kJ | 6.5 | 6.4
Interest rate swaps |  |
Derivative instruments |  |
Volume of forecasted transactions, (in dollars) | $ | $ 346.6 | $ 468.4

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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959 + Details
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