Risk Management Activities and Derivatives Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								3 Months Ended								3 Months Ended																						3 Months Ended
	Mar. 31, 2012 years gal MMBTU	Dec. 31, 2011	Mar. 31, 2012 Derivatives designated as hedging instruments	Dec. 31, 2011 Derivatives designated as hedging instruments	Mar. 31, 2012 Derivatives not designated as hedging instruments	Dec. 31, 2011 Derivatives not designated as hedging instruments	Mar. 31, 2012 Fair value of derivatives not designated as hedging instruments Derivatives not designated as hedging instruments	Dec. 31, 2011 Fair value of derivatives not designated as hedging instruments Derivatives not designated as hedging instruments	Mar. 31, 2012 Interest rate derivatives Derivatives designated as hedging instruments		Mar. 31, 2011 Interest rate derivatives Derivatives designated as hedging instruments		Mar. 31, 2012 Interest rate derivatives Derivative liabilities, current Derivatives designated as hedging instruments	Dec. 31, 2011 Interest rate derivatives Derivative liabilities, current Derivatives designated as hedging instruments	Mar. 31, 2012 Interest rate derivatives Derivative liabilities, long-term Derivatives designated as hedging instruments	Dec. 31, 2011 Interest rate derivatives Derivative liabilities, long-term Derivatives designated as hedging instruments	Mar. 31, 2012 Commodity derivatives Derivatives not designated as hedging instruments		Mar. 31, 2011 Commodity derivatives Derivatives not designated as hedging instruments		Mar. 31, 2012 Commodity derivatives Prepayments and other current assets Derivatives not designated as hedging instruments		Dec. 31, 2011 Commodity derivatives Prepayments and other current assets Derivatives not designated as hedging instruments		Mar. 31, 2012 Commodity derivatives Other assets and deferred debits Derivatives not designated as hedging instruments		Mar. 31, 2012 Commodity derivatives Derivative liabilities, current Derivatives designated as hedging instruments	Dec. 31, 2011 Commodity derivatives Derivative liabilities, current Derivatives designated as hedging instruments	Mar. 31, 2012 Commodity derivatives Derivative liabilities, current Derivatives not designated as hedging instruments		Dec. 31, 2011 Commodity derivatives Derivative liabilities, current Derivatives not designated as hedging instruments		Mar. 31, 2012 Commodity derivatives Derivative liabilities, long-term Derivatives designated as hedging instruments	Dec. 31, 2011 Commodity derivatives Derivative liabilities, long-term Derivatives designated as hedging instruments	Mar. 31, 2012 Commodity derivatives Derivative liabilities, long-term Derivatives not designated as hedging instruments		Dec. 31, 2011 Commodity derivatives Derivative liabilities, long-term Derivatives not designated as hedging instruments		Mar. 31, 2012 CVOs Derivatives not designated as hedging instruments		Dec. 31, 2011 CVOs Other liabilities, current Derivatives not designated as hedging instruments		Mar. 31, 2012 CVOs Other liabilities and deferred credits Derivatives not designated as hedging instruments		Mar. 31, 2012 Fair value loss transition adjustment Derivative liabilities, current Derivatives not designated as hedging instruments	Dec. 31, 2011 Fair value loss transition adjustment Derivative liabilities, current Derivatives not designated as hedging instruments	Mar. 31, 2012 Fair value loss transition adjustment Derivative liabilities, long-term Derivatives not designated as hedging instruments	Dec. 31, 2011 Fair value loss transition adjustment Derivative liabilities, long-term Derivatives not designated as hedging instruments
Economic derivatives
Cash collateral posted	$ 166	$ 147
Notional MMBtu of natural gas	402,800,000
Notional gallons of oil	10,200,000
Interest rate cash flow hedges
Open interest rate hedges mandatory termination dates	2
After-tax (gains) losses in accumulated other comprehensive income	136	141
Next 12 months amount of (gains) losses to reclass to interest expense	13
Notional amount of interest rate cash flow hedges	300	500
Contingent features
Aggregate fair value of instruments in liability position	455
Additional collateral to post	289
Derivatives Fair Value [Line Items]
Derivative asset fair value	8	5			8	5	8	5													7	[1]	5	[1]	1	[1]
Derivative liability fair value	851	802	52	96	799	706	796	703					42	76	7	17											2	2	439	[1]	357	[1]	1	1	354	[1]	332	[1]			14	[2]	3	[2]	1	1	2	2
Derivatives Designated as Hedging Instruments
Amount of Gain or (Loss) Recognized in OCI, Net of Tax on Derivatives									2	[3],[4],[5]	2	[3],[4],[5]
Amount of Gain or (Loss), Net of Tax Reclassified from Accumulated OCI into Income									(3)	[3],[4],[5]	(1)	[3],[4],[5]
Amount of Pre-tax Gain or (Loss) Recognized in Income on Derivatives											(1)	[3],[4],[6]
Derivatives Not Designated As Hedging Instruments
Realized Gain or (Loss)																	(105)	[7]	(52)	[7]
Unrealized Gain or (Loss)																	(206)	[8]	23	[8]
Amount of Gain or (Loss) Recognized in Income on Derivatives																																							$ 8	[9]
Fair Value Of Derivative Instruments Parenthetical Information
CVO's in connection with the acquisition of Florida Progress during 2000	98.6
CVO's repurchased in connection with the negotiated settlement agreement and subsequent tender offer	83.4

[1] Substantially all of these contracts receive regulatory treatment.

[2] As discussed in Note 16 in the 2011 Form 10-K, the Parent issued 98.6 million CVOs in connection with the acquisition of Florida Progress during 2000. Through a negotiated settlement agreement and subsequent tender offer between October 2011 and February 2012, we repurchased and continue to hold 83.4 million CVOs.

[3] Amounts in accumulated OCI related to terminated hedges are reclassified to earnings as the interest expense is recorded. The effective portion of the hedges will be amortized to interest expense over the term of the related debt.

[4] Amounts recorded on the Consolidated Statements of Comprehensive Income are classified in interest charges.

[5] Effective portion.

[6] Related to ineffective portion and amount excluded from effectiveness testing.

[7] After settlement of the derivatives and the fuel is consumed, gains or losses are passed through the fuel cost-recovery clause.

[8] Amounts are recorded in regulatory liabilities and assets, respectively, on the Consolidated Balance Sheets until derivatives are settled.

[9] Amounts recorded in the Consolidated Statements of Comprehensive Income are classified in other, net.