Fair Value Measurements (Reconciliation of Change in Fair Value of Derivatives, Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Realized and unrealized gains (losses):
Realized and unrealized gains (losses) reflected in operating revenues	$ 462		$ 302
Realized and unrealized gains (losses) reflected in interest expense		$ (79)
Unrealized gains (losses) reflected in operating revenues, for derivatives still held at the reporting date	289	328	330
Derivative Financial Instruments, Net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of derivatives based on significant unobservable inputs beginning balance	622	622	566
Realized and unrealized gains (losses):
Realized and unrealized gains (losses) included in earnings	451	(77)	299
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Gain (Loss) Included in Other Comprehensive Income (Loss)	11	18	0
Realized and unrealized gains (losses) included in regulatory assets and liabilities	3	7	0
Purchases	180	55	101
Settlements	(473)	194	(55)
Issuances	(202)	(122)	(173)
Transfers in(b)	(13)	80	(120)
Transfers out(b)	(41)	(155)	4
Fair value of derivatives based on significant unobservable inputs ending balance	538	622	622
The amount of gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to derivatives still held at the reporting date(c)	277	248	329
FPL [Member] | Derivative Financial Instruments, Net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of derivatives based on significant unobservable inputs beginning balance	5	0	2
Realized and unrealized gains (losses):
Realized and unrealized gains (losses) included in earnings	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0	0
Realized and unrealized gains (losses) included in regulatory assets and liabilities	3	7	0
Purchases	0	0	0
Settlements	(8)	(2)	(2)
Issuances	0	0	0
Transfers in(b)	0	0	0
Transfers out(b)	0	0	0
Fair value of derivatives based on significant unobservable inputs ending balance	0	5	0
The amount of gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to derivatives still held at the reporting date(c)	$ 0	$ 0	$ 0