Derivative Instruments (Income Statement Disclosure) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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	$ 231	$ 253
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	137	291
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	45	21
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	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	59	(45)
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)
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	(9)	(10)
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	$ 4	$ (104)