Derivative Instruments (Net Notional Volumes and Additional Disclosures) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013 megawatt-hours
Commodity contract - Power [Member]
Derivative [Line Items]
Non-monetary net notional volumes	(118,000,000)
Commodity contract - Natural gas [Member]
Derivative [Line Items]
Non-monetary net notional volumes	1,262,000,000
Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes	(2,000,000)
Interest rate swaps [Member]
Derivative [Line Items]
Notional amount	7,200
Currency Swap [Member]
Derivative [Line Items]
Notional amount	662
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	846,000,000
FPL [Member] | Commodity contract - Oil [Member]
Derivative [Line Items]
Non-monetary net notional volumes	0