Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	$ 315	$ 312
Special use funds:
Equity securities	2,644	2,674
U.S. Government and municipal bonds	549	612
Corporate debt securities	793	713
Mortgage-backed securities	455	412
Other debt securities	72	52
Other investments:
Equity Securities	30	40
Debt securities	169	171
Derivatives:
Commodity contracts	2,201	1,937
Interest rate contracts	47	34
Derivatives:
Commodity contracts	1,114	982
Interest rate swaps	486	319
Foreign currency swaps	89	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	315	312
Special use funds:
Equity securities	1,280	1,320
U.S. Government and municipal bonds	386	446
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	0
Other investments:
Equity Securities	29	30
Debt securities	8	39
Derivatives:
Commodity contracts	2,604	2,187
Interest rate contracts	0	0
Derivatives:
Commodity contracts	2,574	2,153
Interest rate swaps	0	0
Foreign currency swaps	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	1,364	1,354
U.S. Government and municipal bonds	163	166
Corporate debt securities	793	713
Mortgage-backed securities	455	412
Other debt securities	72	52
Other investments:
Equity Securities	1	10
Debt securities	161	132
Derivatives:
Commodity contracts	2,817	2,540
Interest rate contracts	60	35
Derivatives:
Commodity contracts	2,132	1,887
Interest rate swaps	363	214
Foreign currency swaps	98	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
Derivatives:
Commodity contracts	1,351	1,179
Interest rate contracts	0	0
Derivatives:
Commodity contracts	575	540
Interest rate swaps	127	101
Foreign currency swaps	0	0
Netting [Member] | Fair value measurements made on a recurring basis [Member]
Derivatives:
Commodity contracts	(4,571)	(3,969)
Interest rate contracts	(13)	(1)
Derivatives:
Commodity contracts	(4,167)	(3,598)
Interest rate swaps	(4)	4
Foreign currency swaps	(9)	(5)
FPL [Member] | Fair value measurements made on a recurring basis [Member]
Cash equivalents:
Equity securities	30	36
Special use funds:
Equity securities	1,566	1,598
U.S. Government and municipal bonds	432	480
Corporate debt securities	600	531
Mortgage-backed securities	353	327
Other debt securities	59	40
Derivatives:
Commodity contracts	7	4
Derivatives:
Commodity contracts	257	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	30	36
Special use funds:
Equity securities	320	364
U.S. Government and municipal bonds	295	335
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	0
Derivatives:
Commodity contracts	0	0
Derivatives:
Commodity contracts	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	1,246	1,234
U.S. Government and municipal bonds	137	145
Corporate debt securities	600	531
Mortgage-backed securities	353	327
Other debt securities	59	40
Derivatives:
Commodity contracts	8	1
Derivatives:
Commodity contracts	250	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
Derivatives:
Commodity contracts	3	6
Derivatives:
Commodity contracts	11	6
FPL [Member] | Netting [Member] | Fair value measurements made on a recurring basis [Member]
Derivatives:
Commodity contracts	(4)	(3)
Derivatives:
Commodity contracts	(4)	(3)
Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring [Line Items]
Restricted cash	108	61
Other Current Assets [Member] | FPL [Member]
Fair Value, Assets and Liabilities Measured on Recurring [Line Items]
Restricted cash	$ 30	$ 36