Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivatives:
Derivative assets	$ 1,818	$ 1,971
Derivatives:
Derivative liability	1,370	1,428
Commodity Contract [Member]
Derivatives:
Derivative assets		1,937
Derivatives:
Derivative liability		982
Interest Rate Contract [Member]
Derivatives:
Derivative assets		34
Derivatives:
Derivative liability		319
Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	303	312
Special use funds:
Equity securities	2,719	2,674
U.S. Government and municipal bonds	461	612
Corporate debt securities	861	713
Mortgage-backed securities	502	412
Other debt securities	88	52
Other investments:
Equity Securities	34	40
Debt securities	170	171
Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset, netting	(3,289)	(3,969)
Derivative assets	1,753	1,937
Derivatives:
Derivative liability, netting	(2,975)	(3,598)
Derivative liability	573	982
Fair value measurements made on a recurring basis [Member] | Interest Rate Contract [Member]
Derivatives:
Derivative asset, netting	(9)	(1)
Derivative assets	65	34
Derivatives:
Derivative liability, netting	(6)	4
Derivative liability	755	319
Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative liability, netting	(3)	(5)
Derivative liability	42	127
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	303	312
Special use funds:
Equity securities	1,325	1,320
U.S. Government and municipal bonds	318	446
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	0
Other investments:
Equity Securities	25	30
Debt securities	17	39
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	1,742	2,187
Derivatives:
Derivative liability before netting	1,695	2,153
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair value measurements made on a recurring basis [Member] | Interest Rate Contract [Member]
Derivatives:
Derivative asset before netting	0	0
Derivatives:
Derivative liability before netting	0	0
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative liability before netting	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	0	0
Special use funds:
Equity securities	1,394	1,354
U.S. Government and municipal bonds	143	166
Corporate debt securities	861	713
Mortgage-backed securities	502	412
Other debt securities	88	52
Other investments:
Equity Securities	9	10
Debt securities	153	132
Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	2,037	2,540
Derivatives:
Derivative liability before netting	1,240	1,887
Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member] | Interest Rate Contract [Member]
Derivatives:
Derivative asset before netting	74	35
Derivatives:
Derivative liability before netting	643	214
Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative liability before netting	45	132
Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [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
Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	1,263	1,179
Derivatives:
Derivative liability before netting	613	540
Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [Member] | Interest Rate Contract [Member]
Derivatives:
Derivative asset before netting	0	0
Derivatives:
Derivative liability before netting	118	101
Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative liability before netting	0	0
FPL [Member]
Derivatives:
Derivative assets	48	4
Derivatives:
Derivative liability	9	222
FPL [Member] | Commodity Contract [Member]
Derivatives:
Derivative assets		4
Derivatives:
Derivative liability		222
FPL [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	24	36
Special use funds:
Equity securities	1,627	1,598
U.S. Government and municipal bonds	348	480
Corporate debt securities	651	531
Mortgage-backed securities	393	327
Other debt securities	74	40
FPL [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset, netting	(19)	(3)
Derivative assets	48	4
Derivatives:
Derivative liability, netting	(19)	(3)
Derivative liability	9	222
FPL [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	24	36
Special use funds:
Equity securities	352	364
U.S. Government and municipal bonds	222	335
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	0
FPL [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	0	0
Derivatives:
Derivative liability before netting	0	0
FPL [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	0	0
Special use funds:
Equity securities	1,275	1,234
U.S. Government and municipal bonds	126	145
Corporate debt securities	651	531
Mortgage-backed securities	393	327
Other debt securities	74	40
FPL [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	63	1
Derivatives:
Derivative liability before netting	23	219
FPL [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [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
FPL [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	4	6
Derivatives:
Derivative liability before netting	5	6
Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring [Line Items]
Restricted cash	89	61
Other Current Assets [Member] | FPL [Member]
Fair Value, Assets and Liabilities Measured on Recurring [Line Items]
Restricted cash	$ 24	$ 36