Derivative Instruments (Net Notional Volumes and Additional Disclosures) (Details) bbl in Millions, MWh in Millions, MMBTU in Millions, $ in Millions	Sep. 30, 2015 USD ($) MWh MMBTU bbl	Dec. 31, 2014 USD ($) MWh MMBTU bbl
Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes | MWh	(136)	(73)
Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes | MMBTU	1,363	1,436
Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes | bbl	(9)	(11)
Interest rate contracts [Member]
Derivative [Line Items]
Notional amount	$ 8,100	$ 7,400
Currency Swap [Member]
Derivative [Line Items]
Notional amount	$ 702	$ 661
FPL [Member] | Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes | MWh	0	0
FPL [Member] | Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes | MMBTU	887	845
FPL [Member] | Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes | bbl	0	0