Power purchase agreements and other intangible assets and liabilities (Tables)

12 Months Ended

Dec. 31, 2015

Power purchase agreements and other intangible assets and liabilities.

Schedule of components of intangible assets subject to amortization


		Other Intangible Assets, Net
		Power Purchase			Development
		Agreements			Costs			Total
Gross balances, December 31, 2015		$	534.0		$	12.9		$	546.9
Less: accumulated amortization			(225.4)			(12.6)			(238.0)
Net carrying amount, December 31, 2015		$	308.6		$	0.3		$	308.9


		Other Intangible Assets, Net
		Power Purchase			Development
		Agreements			Costs			Total
Gross balances, December 31, 2014		$	563.6		$	13.4		$	577.0
Less: accumulated amortization			(187.4)			(12.5)			(199.9)
Net carrying amount, December 31, 2014		$	376.2		$	0.9		$	377.1


		Power Purchase and Fuel Supply Agreement Liabilities,Net
		Power Purchase			Fuel Supply
		Agreements			Agreements			Total
Gross balances, December 31, 2015		$	(28.4)		$	(12.6)		$	(41.0)
Less: accumulated amortization			9.1			4.9			14.0
Net carrying amount, December 31, 2015		$	(19.3)		$	(7.7)		$	(27.0)


		Power Purchase and Fuel Supply Agreement Liabilities,Net
		Power Purchase			Fuel Supply
		Agreements			Agreements			Total
Gross balances, December 31, 2014		$	(32.2)		$	(12.6)		$	(44.8)
Less: accumulated amortization			7.7			3.7			11.4
Net carrying amount, December 31, 2014		$	(24.5)		$	(8.9)		$	(33.4)

Schedule of amortization expense of intangible assets


		2015			2014			2013
Power purchase agreements		$	51.3		$	57.6		$	60.6
Fuel supply agreements			(1.2)			(1.2)			(1.2)
Total amortization		$	50.1		$	56.4		$	59.4

Schedule of estimated future amortization expense for the next five years


		Power Purchase			Fuel Supply
Year Ended December 31,		Agreements			Agreements
2016		$	34.9		$	(1.2)
2017			32.9			(1.2)
2018			26.1			(1.2)
2019			25.4			(1.2)
2020			22.4			(1.2)

Schedule of weighted average remaining amortization period related to the entity's intangible assets


		Power Purchase		Fuel Supply
As of December 31, 2015		Agreements		Agreements
(in years)
Weighted average remaining amortization period		7.7		7.6