Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivatives [Abstract]
Derivative Assets	$ 1,919	$ 1,804
Derivatives [Abstract]
Derivative Liabilities	1,191	899
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	486	1,294
Special use funds [Abstract]
Equity securities	3,046	3,314
U.S. Government and municipal bonds	604	617
Corporate debt securities	728	765
Mortgage-backed securities	478	435
Other debt securities	146	129
Other Investments [Abstract]
Equity securities	24	12
Debt securities	126	137
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	486	1,294
Special use funds [Abstract]
Equity securities	1,445	1,595
U.S. Government and municipal bonds	449	478
Corporate debt securities	0	1
Mortgage-backed securities	0	0
Other debt securities	0	0
Other Investments [Abstract]
Equity securities	13	2
Debt securities	36	34
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Current other assets [Member]
Assets [Abstract]
Restricted cash	85	159
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	0	0
Special use funds [Abstract]
Equity securities	1,601	1,719
U.S. Government and municipal bonds	155	139
Corporate debt securities	728	764
Mortgage-backed securities	478	435
Other debt securities	145	129
Other Investments [Abstract]
Equity securities	11	10
Debt securities	90	103
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [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	1	0
Other Investments [Abstract]
Equity securities	0	0
Debt securities	0	0
Commodity contracts [Member] | Fair Value, Measurements, Recurring [Member]
Derivatives [Abstract]
Asset offsetting	(2,811)	(2,225)
Derivative Assets	1,840	1,737
Derivatives [Abstract]
Liability offsetting	(2,622)	(2,225)
Derivative Liabilities	683	567
Commodity contracts [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	1,379	1,303
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	1,329	1,217
Commodity contracts [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	1,923	1,301
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	1,410	915
Commodity contracts [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	1,349	1,358
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	566	660
Interest Rate Contract [Member] | Fair Value, Measurements, Recurring [Member]
Derivatives [Abstract]
Asset offsetting	(7)	5
Derivative Assets	49	55
Derivatives [Abstract]
Liability offsetting	(7)	5
Derivative Liabilities	465	280
Interest Rate Contract [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	0
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	0	0
Interest Rate Contract [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	56	50
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	336	143
Interest Rate Contract [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	0
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	136	132
Currency Swap [Member] | Fair Value, Measurements, Recurring [Member]
Derivatives [Abstract]
Asset offsetting	13	12
Derivative Assets	30	12
Derivatives [Abstract]
Liability offsetting	13	12
Derivative Liabilities	43	52
Currency Swap [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	0
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	0	0
Currency Swap [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	17	0
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	30	40
Currency Swap [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	0
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	0	0
FPL[Member]
Derivatives [Abstract]
Derivative Assets	0	2
Derivatives [Abstract]
Derivative Liabilities	41	2
FPL[Member] | Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	206	144
Special use funds [Abstract]
Equity securities	1,850	2,035
U.S. Government and municipal bonds	470	474
Corporate debt securities	544	539
Mortgage-backed securities	367	333
Other debt securities	132	116
FPL[Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	206	144
Special use funds [Abstract]
Equity securities	398	473
U.S. Government and municipal bonds	350	362
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, Recurring [Member] | Current other assets [Member]
Assets [Abstract]
Restricted cash	81	128
FPL[Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents and restricted cash - equity securities	0	0
Special use funds [Abstract]
Equity securities	1,452	1,562
U.S. Government and municipal bonds	120	112
Corporate debt securities	544	539
Mortgage-backed securities	367	333
Other debt securities	131	116
FPL[Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [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	1	0
FPL[Member] | Commodity contracts [Member] | Fair Value, Measurements, Recurring [Member]
Derivatives [Abstract]
Asset offsetting	(2)	(1)
Derivative Assets	0	2
Derivatives [Abstract]
Liability offsetting	(2)	(1)
Derivative Liabilities	41	2
FPL[Member] | Commodity contracts [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	0
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	0	0
FPL[Member] | Commodity contracts [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	2	1
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	7	1
FPL[Member] | Commodity contracts [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Other Investments [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	2
Derivatives [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	$ 36	$ 2