Fair Value Measurements (Gains and Losses on Available-for-sale Debt Securities) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Debt Securities [Member]
Marketable Securities, Available-for-sale [Line Items]
Realized Gains	$ 17	$ 20	$ 25	$ 28
Realized Losses	11	26	20	40
Proceeds from sale or maturity of securities	788	719	1,475	1,313
Available for sale securities: Special Use Funds - Debt Securities [Member]
Marketable Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	69		69		$ 14
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	11		11		52
Fair value of available for sale securities in an unrealized loss position	284		284		1,273
FPL [Member] \| Debt Securities [Member]
Marketable Securities, Available-for-sale [Line Items]
Realized Gains	9	15	15	20
Realized Losses	5	20	9	29
Proceeds from sale or maturity of securities	685	$ 653	1,227	$ 1,042
FPL [Member] \| Available for sale securities: Special Use Funds - Debt Securities [Member]
Marketable Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	53		53		11
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8		8		41
Fair value of available for sale securities in an unrealized loss position	$ 205		$ 205		$ 961

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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