Fair Value Measurements (Gains and Losses on Available-for-sale Debt Securities) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Debt Securities [Member]
Marketable Securities, Available-for-sale [Line Items]
Realized Gains	$ 30	$ 9
Realized Losses	17	9
Proceeds from sale or maturity of securities	738	687
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	89		$ 75
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	82		7
Fair value of available for sale securities in an unrealized loss position	603		314
FPL [Member] \| Debt Securities [Member]
Marketable Securities, Available-for-sale [Line Items]
Realized Gains	25	5
Realized Losses	15	4
Proceeds from sale or maturity of securities	607	$ 543
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	70		58
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	66		7
Fair value of available for sale securities in an unrealized loss position	$ 448		$ 240

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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-SubTopic 10
-Section 50
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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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