Fair Value Measurements (Reconciliation of Changes in the Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value based on significant unobservable inputs, beginning balance	$ 532	$ 544	$ 538	$ 622
Realized and unrealized gains (losses): [Abstract]
Included in Earnings	153	115	373	369
Included in other comprehensive income			(3)	8
Included in regulatory assets and liabilities	0	(1)	0	3
Purchases	28	42	203	125
Settlements	(72)	(109)	(300)	(376)
Issuances	(16)	(32)	(159)	(164)
Transfers in	1	3	4	(15)
Transfers out	36	(16)	6	(26)
Fair value based on significant unobservable inputs, ending balance	662	546	662	546
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	150	107	231	260
Realized and unrealized gains (losses) reflected in operating revenues	198	131	443	379
Unrealized gains (losses) reflected in operating revenues related to derivatives still held at the reporting date	194	123	302	271
FPL [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value based on significant unobservable inputs, beginning balance	(1)	4	0	5
Realized and unrealized gains (losses): [Abstract]
Included in Earnings	0	0	0	0
Included in other comprehensive income			0	0
Included in regulatory assets and liabilities	0	(1)	0	3
Purchases	0	0	0	0
Settlements	1	(1)	0	(6)
Issuances	0	0	0	0
Transfers in	0	0	0	0
Transfers out	0	0	0	0
Fair value based on significant unobservable inputs, ending balance	0	2	0	2
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	$ 0	$ 0	$ 0	$ 0