Derivative Instruments (Net Notional Volumes and Additional Disclosures) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013 MWh	Dec. 31, 2012 MWh
Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes	(110,000,000)	(77,000,000)
Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes	1,174,000,000	1,293,000,000
Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes	(10,000,000)	(8,000,000)
Interest rate contracts [Member]
Derivative [Line Items]
Notional amount	$ 7,600	$ 7,300
Currency Swap [Member]
Derivative [Line Items]
Notional amount	$ 662	$ 662
FPL [Member] | Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes	0	0
FPL [Member] | Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes	705,000,000	894,000,000
FPL [Member] | Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes	0	0