Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale debt securities.

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Amount of the cumulative effect on retained earnings net of related income tax effect.

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Fair Value Measurements (Available for Sale Securities) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Realized Gains		$ 8	$ 55
Realized Losses		14	29
Proceeds from Sale and Maturity of Available-for-sale Securities		595	626
Unrealized losses on available for sale debt securities		32		$ 12
Fair value of available for sale securities in an unrealized loss position		1,295		918
available for sale securities: Special Use Funds - Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains		18		37
FPL [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized Gains		5	13
Realized Losses		9	19
Proceeds from Sale and Maturity of Available-for-sale Securities		389	$ 441
Unrealized losses on available for sale debt securities		25		9
Fair value of available for sale securities in an unrealized loss position		1,008		670
FPL [Member] \| available for sale securities: Special Use Funds - Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains		$ 15		$ 28
AOCI Including Portion Attributable to Noncontrolling Interest [Member] \| Accounting Standards Update 2016-01 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax	$ (312)