Commitments and Contingencies (Insurance and Legal Proceedings) (Details) - USD ($)	24 Months Ended
	Dec. 31, 1996	Jun. 30, 2016	Jan. 29, 1999
Insurance [Abstract]
Maximum obtainable amount of private liability insurance available under Price-Anderson Act		$ 375,000,000
Amount of secondary financial protection liability insurance coverage per incident		13,000,000,000
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 inusurance mutal companies for property damage decontamination and premature decommissioning risks		1,500,000,000
Potential amount of retrospective assessment per occurrence per site for property damage, decontamination and premature decommissioning risks		187,000,000
Legal Proceedings [Abstract]
Shares of Adelphia common stock purchased (in shares)	1,091,524
Shares of Adelphia preferred stock purchased (in shares)	20,000
Shares of Adelphia common stock if Adelphia preferred stock converted to Adelphia common stock (in shares)	2,358,490
Aggregate price paid for Adelphia common and preferred stock	$ 35,900,000
Cash paid by Adelphia for repurchase of Adelphia acquired shares			$ 149,213,130
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		113,000,000
Seabrook Station Insurance [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		3,000,000
Duane Arnold Energy Center Insurance [Member]
Insurance [Abstract]
Potential retrospective assessment recoverable from minority interest for nuclear liability secondary financial protection		38,000,000
Potential retrospective assessment recoverable from minority interest for property damage, decontamination and premature decommissioning risks		5,000,000
St Lucie Unit No 2 Insurance [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