v2.4.0.6

Accounting for derivative instruments and hedging activities (Details 2) In Thousands, unless otherwise specified | Dec. 31, 2012 Natural gas swaps MMBTU | Dec. 31, 2011 Natural gas swaps MMBTU | Dec. 31, 2012 Gas purchase agreements gigajoule | Dec. 31, 2012 Interest rate swaps USD ($) | Dec. 31, 2011 Interest rate swaps USD ($) | Dec. 31, 2012 Currency forward CAD | Dec. 31, 2011 Currency forward CAD
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Derivative instruments |  |  |  |  |  |  |
Volume of forecasted transactions | 10,640,000 | 14,140,000 | 49,810,000 |  |  |  |
Volume of forecasted transactions, (in dollars) |  |  |  | $ 140,154 | $ 52,711 | 176,550 | 312,533

X
- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + 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 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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- Details
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