Commitments and Contingencies (Insurance) (Details)	3 Months Ended
	Mar. 31, 2018 USD ($)
Insurance [Abstract]
Maximum obtainable amount of private liability insurance available under Price-Anderson Act	$ 450,000,000
Amount of secondary financial protection liability insurance coverage per incident	12,600,000,000
Potential retrospective assessments under secondary financial protection system	1,000,000,000
Potential retrospective assessments under secondary financial protection system payable per incident per year	152,000,000
Amount of coverage per occurrence per site for property damage, decontamination and premature decommissioning risks	2,750,000,000
Amount of sublimit for nonnuclear perils per occurrence per site under nuclear insurance mutual companies for property damage decontamination and premature decommissioning risks	$ 1,500,000,000
Coinsurance, percent	10.00%
Coinsurance, limit of coverage per loss per site occurrence	$ 400,000,000
Potential amount of retrospective assessment per occurrence per site for property damage, decontamination and premature decommissioning risks	177,000,000
FPL [Member]
Insurance [Abstract]
Potential retrospective assessments under secondary financial protection system	509,000,000
Potential retrospective assessments under secondary financial protection system payable per incident per year	76,000,000
Potential amount of retrospective assessment per occurrence per site for property damage, decontamination and premature decommissioning risks	108,000,000
Seabrook Station [Member]
Insurance [Abstract]
Potential retrospective assessment recoverable from minority interest for nuclear liability secondary financial protection	15,000,000
Potential retrospective assessment recoverable from minority interest for property damage, decontamination and premature decommissioning risks	2,000,000
Duane Arnold Energy Center [Member]
Insurance [Abstract]
Potential retrospective assessment recoverable from minority interest for nuclear liability secondary financial protection	38,000,000
Amount of sublimit for nonnuclear perils per occurrence per site under nuclear insurance mutual companies for property damage decontamination and premature decommissioning risks	1,000,000,000
Potential retrospective assessment recoverable from minority interest for property damage, decontamination and premature decommissioning risks	5,000,000
St Lucie Unit No. 2 [Member]
Insurance [Abstract]
Potential retrospective assessment recoverable from minority interest for nuclear liability secondary financial protection	19,000,000
Potential retrospective assessment recoverable from minority interest for property damage, decontamination and premature decommissioning risks	$ 4,000,000