Fair Value Measurements (Reconciliation of Change in Fair Value of Derivatives, Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Realized and unrealized gains (losses):
Realized and unrealized gains (losses) reflected in operating revenues	$ 397	$ 462
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	283	289	328
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	538	622	622
Realized and unrealized gains (losses):
Realized and unrealized gains (losses) included in earnings	333	451	(77)
Realized and unrealized gains (losses) included in other comprehensive income (loss)	8	11	18
Realized and unrealized gains (losses) included in regulatory assets and liabilities	1	3	7
Purchases	261	180	55
Settlements	(390)	(473)	194
Issuances	(195)	(202)	(122)
Transfers in(b)	19	(13)	80
Transfers out(b)	3	(41)	(155)
Fair value of derivatives based on significant unobservable inputs ending balance	578	538	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)	219	277	248
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	0	5	0
Realized and unrealized gains (losses):
Realized and unrealized gains (losses) included in earnings	0	0	0
Realized and unrealized gains (losses) included in other comprehensive income (loss)	0	0	0
Realized and unrealized gains (losses) included in regulatory assets and liabilities	1	3	7
Purchases	0	0	0
Settlements	0	(8)	(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	1	0	5
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