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The estimated net amount of existing gains (losses) on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Derivative Instruments (Details) (USD $) In Millions	6 Months Ended	12 Months Ended				6 Months Ended										6 Months Ended
Derivative Instruments (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Interest Rate Swaps	Feb. 28, 2011 Interest Rate Swaps	Dec. 31, 2010 Interest Rate Swaps	Jun. 30, 2011 Commodity contract	Dec. 31, 2010 Commodity contract	Jun. 30, 2011 Power contracts	Dec. 31, 2010 Power contracts	Jun. 30, 2011 Gas contracts	Dec. 31, 2010 Gas contracts	Jun. 30, 2011 Coal contracts	Dec. 31, 2010 Coal contracts	Jun. 30, 2011 Other commodity contracts	Dec. 31, 2010 Other commodity contracts	Jun. 30, 2011 Interest rate contracts	Dec. 31, 2010 Interest rate contracts	Jun. 30, 2011 Foreign exchange contracts	Dec. 31, 2010 Foreign exchange contracts
Derivatives, Fair Value
Net unrealized pre-tax gain (loss) on cash-flow hedges recorded in Accumulated other comprehensive loss						$ (312.5)	$ (388.0)									$ 8.8	$ 10.1
Cash flow hedge gain (loss) to be reclassified within twelve months						(156.8)										0.1
Notional amount, interest rate swap fair value hedge			550		400
Unrealized gain (loss), fair value of interest rate swap fair value hedge			35.3		35.7
Notional amount, interest rate swap not qualify as fair value hedges				150
Asset values, derivatives designated as hedging instruments for accounting purposes	2,514.9	3,202.9						1,018.7	1,167.9	1,405.9	1,902.3	55.0	97.0			35.3	35.7
Liability values, derivatives designated as hedging instruments for accounting purposes	(2,501.7)	(3,244.2)						(1,037.6)	(1,362.8)	(1,432.1)	(1,832.8)	(32.0)	(48.6)
Asset values, derivatives not designated as hedging instruments for accounting purposes	7,770.9	10,557.9						4,573.0	6,795.0	2,682.9	3,390.1	154.7	266.0	305.9	61.4	40.7	34.4	13.7	11.0
Liability values, derivatives not designated as hedging instruments for accounting purposes	(7,983.0)	(10,687.2)						(4,977.8)	(7,166.5)	(2,516.5)	(3,155.3)	(142.8)	(259.7)	(299.8)	(61.6)	(37.9)	(35.7)	(8.2)	(8.4)
Asset values, all derivatives combined	10,285.8	13,760.8						5,591.7	7,962.9	4,088.8	5,292.4	209.7	363.0	305.9	61.4	76.0	70.1	13.7	11.0
Liability values, all derivatives combined	(10,484.7)	(13,931.4)						(6,015.4)	(8,529.3)	(3,948.6)	(4,988.1)	(174.8)	(308.3)	(299.8)	(61.6)	(37.9)	(35.7)	(8.2)	(8.4)
Netting arrangements, assets	(9,717.9)	(12,955.5)
Netting arrangements, liabilities	9,717.9	12,955.5
Cash collateral, assets	(58.8)	(28.4)
Cash collateral, liabilities	2.5	0.6
Net fair values, derivative assets	509.1	776.9
Net fair values, derivative liabilities	(764.3)	(975.3)
Derivatives classified as accounts receivable	(72.7)	(16.4)
Derivative assets, current	324.3	534.4
Derivative liabilities, current	(494.2)	(622.3)
Derivative assets, noncurrent	257.5	258.9
Derivative liabilities, noncurrent	$ (270.1)	$ (353.0)