Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	$ 312	$ 32
Special use funds [Abstract]
Equity securities	2,674	2,634
U.S. Government and municipal bonds	612	711
Corporate debt securities	713	704
Mortgage-backed securities	412	493
Other debt securities	52	57
Other Investments [Abstract]
Equity securities	40	36
Debt securities	171	175
Derivatives [Abstract]
Commodity contracts	1,937	1,949
Interest rate contracts	34	50
Derivatives [Abstract]
Commodity contracts	982	1,358
Interest rate contracts	319	266
Foreign currency swaps	127	131
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	312	32
Special use funds [Abstract]
Equity securities	1,320	1,217
U.S. Government and municipal bonds	446	520
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	25
Other Investments [Abstract]
Equity securities	30	35
Debt securities	39	5
Derivatives [Abstract]
Commodity contracts	2,187	1,801
Interest rate contracts	0	0
Derivatives [Abstract]
Commodity contracts	2,153	1,720
Interest rate contracts	0	0
Foreign currency swaps	0	0
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Current other assets [Member]
Assets [Abstract]
Restricted cash	61
Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	0	0
Special use funds [Abstract]
Equity securities	1,354	1,417
U.S. Government and municipal bonds	166	191
Corporate debt securities	713	704
Mortgage-backed securities	412	493
Other debt securities	52	32
Other Investments [Abstract]
Equity securities	10	1
Debt securities	132	170
Derivatives [Abstract]
Commodity contracts	2,540	3,177
Interest rate contracts	35	35
Derivatives [Abstract]
Commodity contracts	1,887	3,150
Interest rate contracts	214	126
Foreign currency swaps	132	131
Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	0	0
Special use funds [Abstract]
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 [Abstract]
Equity securities	0	0
Debt securities	0	0
Derivatives [Abstract]
Commodity contracts	1,179	1,167
Interest rate contracts	0	0
Derivatives [Abstract]
Commodity contracts	540	420
Interest rate contracts	101	125
Foreign currency swaps	0	0
Netting [Member]
Derivatives [Abstract]
Commodity contracts	(3,969)	(4,196)
Interest rate contracts	(1)	15
Derivatives [Abstract]
Commodity contracts	(3,598)	(3,932)
Interest rate contracts	4	15
Foreign currency swaps	(5)	0
FPL [Member]
Special use funds [Abstract]
Equity securities	1,598	1,561
U.S. Government and municipal bonds	480	600
Corporate debt securities	531	501
Mortgage-backed securities	327	422
Other debt securities	40	45
Derivatives [Abstract]
Commodity contracts	4	7
Derivatives [Abstract]
Commodity contracts	222	370
FPL [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	36
Special use funds [Abstract]
Equity securities	364	324
U.S. Government and municipal bonds	335	435
Corporate debt securities	0	0
Mortgage-backed securities	0	0
Other debt securities	0	25
Derivatives [Abstract]
Commodity contracts	0	0
Derivatives [Abstract]
Commodity contracts	0	0
FPL [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Current other assets [Member]
Assets [Abstract]
Restricted cash	36
FPL [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	0
Special use funds [Abstract]
Equity securities	1,234	1,237
U.S. Government and municipal bonds	145	165
Corporate debt securities	531	501
Mortgage-backed securities	327	422
Other debt securities	40	20
Derivatives [Abstract]
Commodity contracts	1	2
Derivatives [Abstract]
Commodity contracts	219	370
FPL [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	0
Special use funds [Abstract]
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 [Abstract]
Commodity contracts	6	6
Derivatives [Abstract]
Commodity contracts	6	1
FPL [Member] | Netting [Member]
Derivatives [Abstract]
Commodity contracts	(3)	(1)
Derivatives [Abstract]
Commodity contracts	$ (3)	$ (1)