v3.20.1

Accounting for derivative instruments and hedging activities - gain, loss (Details) - Derivative instruments not designated as cash flow hedges - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2020 | Mar. 31, 2019
Gas and Interest Rate Swaps |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Unrealized gain (loss) resulting from changes in the fair value of derivative financial instruments | $ (5.6) | $ (2.4)
Natural gas swaps |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Realized loss (gain) for derivative instruments | 0.7 | (0.3)
Natural gas swaps | Change in fair value of derivatives |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Unrealized gain (loss) resulting from changes in the fair value of derivative financial instruments | (0.5) | 0.2
Gas purchase agreements |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Realized loss (gain) for derivative instruments | 2.2 | 2.0
Gas purchase agreements | Change in fair value of derivatives |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Unrealized gain (loss) resulting from changes in the fair value of derivative financial instruments | 1.0 | (0.4)
Interest rate swaps |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Realized loss (gain) for derivative instruments | 0.3 | (1.3)
Interest rate swaps | Change in fair value of derivatives |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Unrealized gain (loss) resulting from changes in the fair value of derivative financial instruments | (6.1) | (2.2)
Convertible Debentures | Other (income) expense, net |  |
Impact of derivative instruments on the consolidated statements of operations |  |
Unrealized gain (loss) resulting from changes in the fair value of derivative financial instruments | $ 2.6 | $ 4.7

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- Definition The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13(h)) -URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260 + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 + Details
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