Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivatives:
Derivative assets	$ 1,974	$ 2,235
Derivatives:
Derivative liability	784	881
Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	359	982
Special use funds:
Equity securities	3,168	2,913
U.S. Government and municipal bonds	516	466
Corporate debt securities	804	764
Mortgage-backed securities	458	498
Other debt securities	117	81
Other investments:
Equity Securities	33	35
Debt securities	144	161
Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset, netting	(2,595)	(2,652)
Derivative assets	1,814	1,938
Derivatives:
Derivative liability, netting	(2,454)	(2,485)
Derivative liability	429	483
Fair value measurements made on a recurring basis [Member] | Interest Rate Contract [Member]
Derivatives:
Derivative asset, netting	(2)	8
Derivative assets	152	296
Derivatives:
Derivative liability, netting	(2)	8
Derivative liability	304	292
Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative asset, netting	8	0
Derivative assets	8	1
Derivatives:
Derivative liability, netting	8	0
Derivative liability	51	106
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	359	982
Special use funds:
Equity securities	1,547	1,410
U.S. Government and municipal bonds	354	296
Corporate debt securities	1	1
Mortgage-backed securities	0	0
Other debt securities	0	0
Other investments:
Equity Securities	23	26
Debt securities	7	8
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	1,543	1,563
Derivatives:
Derivative liability before netting	1,461	1,476
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 asset before netting	0	0
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	1,621	1,503
U.S. Government and municipal bonds	162	170
Corporate debt securities	803	763
Mortgage-backed securities	458	498
Other debt securities	117	81
Other investments:
Equity Securities	10	9
Debt securities	137	153
Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset before netting	1,541	1,827
Derivatives:
Derivative liability before netting	938	980
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	154	285
Derivatives:
Derivative liability before netting	189	171
Significant Other Observable Inputs (Level 2) [Member] | Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative asset before netting	0	1
Derivatives:
Derivative liability before netting	43	106
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	1,325	1,200
Derivatives:
Derivative liability before netting	484	512
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	3
Derivatives:
Derivative liability before netting	117	113
Significant Unobservable Inputs (Level 3) [Member] | Fair value measurements made on a recurring basis [Member] | Foreign Currency Swap [Member]
Derivatives:
Derivative asset before netting	0	0
Derivatives:
Derivative liability before netting	0	0
Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring [Line Items]
Restricted cash	142	164
FPL [Member]
Derivatives:
Derivative assets	18	209
Derivatives:
Derivative liability	2	1
FPL [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	104	120
Special use funds:
Equity securities	1,902	1,745
U.S. Government and municipal bonds	388	362
Corporate debt securities	575	547
Mortgage-backed securities	351	384
Other debt securities	106	70
FPL [Member] | Fair value measurements made on a recurring basis [Member] | Commodity Contract [Member]
Derivatives:
Derivative asset, netting	(9)	(3)
Derivative assets	18	209
Derivatives:
Derivative liability, netting	(9)	(3)
Derivative liability	2	1
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	104	120
Special use funds:
Equity securities	424	373
U.S. Government and municipal bonds	253	221
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	1,478	1,372
U.S. Government and municipal bonds	135	141
Corporate debt securities	575	547
Mortgage-backed securities	351	384
Other debt securities	106	70
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	26	208
Derivatives:
Derivative liability before netting	8	1
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	1	4
Derivatives:
Derivative liability before netting	3	3
FPL [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring [Line Items]
Restricted cash	$ 92	$ 120