Derivative Instruments (Balance Sheet Disclosure) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 1,958	$ 1,999
Derivative Liability	1,343	1,755
Current derivative assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	654	990
Derivative Asset, Collateral, Obligation to Return Cash, Offset	231	197
Non Current Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	1,304	1,009
Derivative Asset, Collateral, Obligation to Return Cash, Offset	173	97
Current derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	734	1,289
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	65	20
Noncurrent derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	609	466
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	14	10
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	1,903	1,949
Derivative Liability	866	1,358
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	55	50
Derivative Liability	340	266
Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	0
Derivative Liability	137	131
FPL [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	5	7
Derivative Liability	235	370
FPL [Member] \| Current derivative assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	4	6
FPL [Member] \| Non Current Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	1	1
FPL [Member] \| Current derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	216	370
FPL [Member] \| Noncurrent derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	19
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	53	35
Derivative Liability, Fair Value, Gross Liability	360	257
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,710	6,145
Derivative Liability, Fair Value, Gross Liability	4,463	5,415
Commodity Contract [Member] \| FPL [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	5	7
Derivative Liability	235	370
Commodity Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| FPL [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,710	6,145
Derivative Liability, Fair Value, Gross Liability	4,348	5,290
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| FPL [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6	8
Derivative Liability, Fair Value, Gross Liability	236	371
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	53	35
Derivative Liability, Fair Value, Gross Liability	223	126
Interest Rate Contract [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	115	125
Foreign Exchange Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	137	131
Foreign Exchange Contract [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	$ 0	$ 0

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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