v2.4.0.8

Derivative instruments and hedging activities (Details 5) (Derivative instruments not designated as cash flow hedges, USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012
Unrealized gains and (losses) |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | $ (24.3) | $ 4.7 | $ (36.9) | $ 62.0
Natural gas swaps | Unrealized gains and (losses) |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | 1.1 | 0.5 | 0.7 | 1.4
Gas purchase agreements | Realized (gains) and losses |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | 14.1 | 13.2 | 30.4 | 16.0
Gas purchase agreements | Unrealized gains and (losses) |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | (7.4) | 1.2 | (15.5) | 59.1
Interest rate swaps | Realized (gains) and losses |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | 4.0 | 1.1 | 6.6 | 2.2
Interest rate swaps | Unrealized gains and (losses) |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | (18.0) | 3.0 | (22.1) | 1.5
Foreign currency forward contracts | Realized (gains) and losses |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | (10.8) | (3.1) | (13.3) | (15.0)
Foreign currency forward contracts | Unrealized gains and (losses) |  |  |  |
Impact of derivative instruments on the consolidated statements of operations |  |  |  |
Gains and losses for derivative instruments | $ 12.8 | $ 7.7 | $ 18.8 | $ 12.9

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- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959 + Details
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