Derivative Instruments (Income Statement Disclosure) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Not Designated as Hedging Instrument [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 53	$ 202	$ 238	$ 0
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Gains (losses) included in operating revenues [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	114	264	538	502
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Gains (losses) included in fuel, purchased power and interchange [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	1	0	(1)
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Gain Loss Included In Interest Expense Member
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(41)	(58)	(232)	(515)
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Gain Loss Included In Interest Expense Member
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(4)	15	53	96
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Gains (Losses) Included In Other - Net [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(2)	1	(5)	(2)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Gain Loss Included In Interest Expense Member
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Interest Expense	(13)	(18)	(36)	(71)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Gain Loss Included In Interest Expense Member
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Interest Expense	(1)	(3)	(80)	(9)
FPL [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]
Gains (losses) on commodity contracts, recorded as regulatory assets and or liabilities on the balance sheet due to regulatory treatment	$ (12)	$ (35)	$ (164)	$ 35