Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) (Fair value measurements made on a recurring basis [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Cash equivalents:
Equity securities	$ 18	$ 32
Special use funds:
Equity securities	2,672	2,634
U.S. Government and municipal bonds	706	711
Corporate debt securities	748	704
Mortgage-backed securities	493	493
Other debt securities	68	57
Other investments:
Equity Securities	36	36
Debt securities	185	175
Derivatives:
Commodity contracts	1,975	1,949
Interest rate contracts	49	50
Derivatives:
Commodity contracts	1,204	1,358
Interest rate swaps	305	266
Foreign currency swaps	135	131
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member]
Cash equivalents:
Equity securities	18	32
Special use funds:
Equity securities	1,231	1,217
U.S. Government and municipal bonds	494	520
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	26	25
Other investments:
Equity Securities	35	35
Debt securities	9	5
Derivatives:
Commodity contracts	1,618	1,801
Interest rate contracts	0	0
Derivatives:
Commodity contracts	1,583	1,720
Interest rate swaps	0	0
Foreign currency swaps	0	0
Significant Other Observable Inputs (Level 2) [Member]
Cash equivalents:
Equity securities	0	0
Special use funds:
Equity securities	1,441	1,417
U.S. Government and municipal bonds	212	191
Corporate debt securities	748	704
Mortgage-backed securities	493	493
Other debt securities	42	32
Other investments:
Equity Securities	1	1
Debt securities	176	170
Derivatives:
Commodity contracts	3,186	3,177
Interest rate contracts	46	35
Derivatives:
Commodity contracts	2,843	3,150
Interest rate swaps	175	126
Foreign currency swaps	135	131
Significant Unobservable Inputs (Level 3) [Member]
Cash equivalents:
Equity securities	0	0
Special use funds:
Equity securities	0	0
U.S. Government and municipal bonds	0	0
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	0
Other investments:
Equity Securities	0	0
Debt securities	0	0
Derivatives:
Commodity contracts	1,049	1,167
Interest rate contracts	0	0
Derivatives:
Commodity contracts	471	420
Interest rate swaps	127	125
Foreign currency swaps	0	0
Netting [Member]
Derivatives:
Commodity contracts	(3,878)	(4,196)
Interest rate contracts	3	15
Derivatives:
Commodity contracts	(3,693)	(3,932)
Interest rate swaps	3	15
Foreign currency swaps	0	0
FPL [Member]
Special use funds:
Equity securities	1,578	1,561
U.S. Government and municipal bonds	590	600
Corporate debt securities	539	501
Mortgage-backed securities	423	422
Other debt securities	58	45
Derivatives:
Commodity contracts	5	7
Derivatives:
Commodity contracts	376	370
FPL [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member]
Special use funds:
Equity securities	319	324
U.S. Government and municipal bonds	415	435
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	26	25
Derivatives:
Commodity contracts	0	0
Derivatives:
Commodity contracts	0	0
FPL [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Special use funds:
Equity securities	1,259	1,237
U.S. Government and municipal bonds	175	165
Corporate debt securities	539	501
Mortgage-backed securities	423	422
Other debt securities	32	20
Derivatives:
Commodity contracts	3	2
Derivatives:
Commodity contracts	373	370
FPL [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Special use funds:
Equity securities	0	0
U.S. Government and municipal bonds	0	0
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	0
Derivatives:
Commodity contracts	4	6
Derivatives:
Commodity contracts	5	1
FPL [Member] \| Netting [Member]
Derivatives:
Commodity contracts	(2)	(1)
Derivatives:
Commodity contracts	$ (2)	$ (1)

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+ References

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. This item represents interest rate swaps entered into and existing as of the balance sheet date.

+ References

No definition available.

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- Definition

Other Investments Debt Securities Fair Value Disclosure

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. This element represents equity securities of other investments, excluding those held in special use funds.

+ References

No definition available.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. This element represents corporate debt securities of special use funds.

+ References

No definition available.

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+ References

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+ References

No definition available.

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+ References

No definition available.

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+ References

No definition available.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

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- Definition

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

+ References

No definition available.

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