Accounting for derivative instruments and hedging activities (Tables)

12 Months Ended

Dec. 31, 2015

Accounting for derivative instruments and hedging activities

Schedule of notional volumes of forecasted transactions


				December 31,		December 31,
		Units		2015		2014
Natural gas swaps		Natural Gas (Mmbtu)		2.8		6.3
Gas purchase agreements		Natural Gas (Gigajoules)		25.0		33.9
Interest rate swaps		Interest (US$)		302.3		333.9

Schedule of fair value of derivative instruments


		December 31, 2015
		Derivative			Derivative
		Assets			Liabilities
Derivative instruments designated as cash flow hedges:
Interest rate swaps current		$	—		$	1.0
Interest rate swaps long-term			—			2.7
Total derivative instruments designated as cash flow hedges			—			3.7
Derivative instruments not designated as cash flow hedges:
Interest rate swaps current			—			2.0
Interest rate swaps long-term			0.3			7.8
Natural gas swaps current			—			5.0
Gas purchase agreements current			—			28.7
Gas purchase agreements long-term			—			10.3
Total derivative instruments not designated as cash flow hedges			0.3			53.8
Total derivative instruments		$	0.3		$	57.5


		December 31, 2014
		Derivative			Derivative
		Assets			Liabilities
Derivative instruments designated as cash flow hedges:
Interest rate swaps current		$	—		$	1.1
Interest rate swaps long-term			—			2.9
Total derivative instruments designated as cash flow hedges			—			4.0
Derivative instruments not designated as cash flow hedges:
Interest rate swaps current			—			2.0
Interest rate swaps long-term			1.1			6.9
Natural gas swaps current			—			4.4
Natural gas swaps long-term			—			2.2
Gas purchase agreements current			—			28.6
Gas purchase agreements long-term			—			35.5
Total derivative instruments not designated as cash flow hedges			1.1			79.6
Total derivative instruments		$	1.1		$	83.6

Schedule of changes in OCI attributable to derivative financial instruments


		Interest Rate
For the year ended December 31, 2015		Swaps
Accumulated OCI balance at January 1, 2015		$	0.1
Change in fair value of cash flow hedges			(0.6)
Realized from OCI during the period			0.7
Accumulated OCI balance at December 31, 2015		$	0.2
Gains expected to be realized from OCI in the next 12 months, net of $0.6 million of tax		$	0.8


		Interest Rate
For the year ended December 31, 2014		Swaps
Accumulated OCI balance at January 1, 2014		$	0.2
Change in fair value of cash flow hedges			(1.0)
Realized from OCI during the period			0.9
Accumulated OCI balance at December 31, 2014		$	0.1
Gains expected to be realized from OCI in the next 12 months, net of $0.6 million of tax		$	0.9


		Interest Rate			Natural Gas
For the year ended December 31, 2013		Swaps			Swaps			Total
Accumulated OCI balance at January 1, 2013		$	(1.5)		$	0.1		$	(1.4)
Change in fair value of cash flow hedges			0.7			—			0.7
Realized from OCI during the period			1.0			(0.1)			0.9
Accumulated OCI balance at December 31, 2013		$	0.2		$	—		$	0.2
Gains expected to be realized from OCI in the next 12 months, net of $0.6 million of tax		$	0.9		$	—		$	0.9

Summary of realized loss (gain) for derivative instruments not designated as cash flow hedges



		Classification of loss (gain)		Year Ended December 31,
		recognized in income		2015			2014			2013
Gas purchase agreements		Fuel		$	47.3		$	52.4		$	56.5
Natural gas swaps		Fuel			6.0			4.3			—
Interest rate swaps		Interest, net			3.8			6.1			3.4
Foreign currency forwards		Foreign exchange loss (gain)			—			0.5			(14.4)

Summary of the unrealized loss (gain) resulting from changes in the fair value of derivative financial instruments that are not designated as cash flow hedges


		Classification of gain (loss)		Year ended December 31,
		recognized in income		2015			2014			2013
Natural gas swaps		Change in fair value of derivatives		$	1.0		$	(3.3)		$	(0.7)
Gas purchase agreements		Change in fair value of derivatives			16.1			11.6			19.2
Interest rate swaps		Change in fair value of derivatives			(1.7)			(1.5)			7.0
				$	15.4		$	6.8		$	25.5
Foreign currency forwards		Foreign exchange loss		$	—		$	(1.1)		$	(19.4)