Fair Value Measurements (Available for Sale Securities) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Realized Gains	$ 22	$ 98
Realized Losses	18	69
Proceeds from Sale and Maturity of Available-for-sale Securities	701	729
Unrealized losses on available for sale debt securities	36		$ 51
Fair value of available for sale securities in an unrealized loss position	428		1,129
FPL [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized Gains	10	68
Realized Losses	10	61
Proceeds from Sale and Maturity of Available-for-sale Securities	530	$ 589
Unrealized losses on available for sale debt securities	33		45
Fair value of available for sale securities in an unrealized loss position	370		861
Available For Sale Securities: Special Use Funds - Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains	1,183		1,166
Available For Sale Securities: Special Use Funds - Equity Securities [Member] \| FPL [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains	874		863
available for sale securities: Special Use Funds - Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains	41		17
available for sale securities: Special Use Funds - Debt Securities [Member] \| FPL [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains	$ 31		$ 14

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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