Derivative Instruments (Net Notional Volumes and Additional Disclosures) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012 megawatt-hours
Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes	(46,000,000)
Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes	1,221,000,000
Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes	(7,000,000)
Interest rate swaps [Member]
Derivative [Line Items]
Notional amount	6,900
Currency Swap [Member]
Derivative [Line Items]
Notional amount	544
FPL [Member] | Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes	0
FPL [Member] | Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes	837,000,000
FPL [Member] | Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes	0