Fair Value Measurements (Reconciliation of Changes in the Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value based on significant unobservable inputs, beginning balance	$ 578	$ 538
Realized and unrealized gains (losses): [Abstract]
Included in Earnings	216	254
Included in other comprehensive income	(1)	(6)
Included in regulatory assets and liabilities	(2)	(3)
Purchases	21	100
Settlements	(85)	(133)
Issuances	(16)	(74)
Transfers in	9	3
Transfers out	(5)	(30)
Fair value based on significant unobservable inputs, ending balance	715	649
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	141	196
Realized and unrealized gains (losses) reflected in operating revenues	215	274
Unrealized gains (losses) reflected in operating revenues related to derivatives still held at the reporting date	141	216
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	0
Realized and unrealized gains (losses): [Abstract]
Included in Earnings	0	0
Included in other comprehensive income	0	0
Included in regulatory assets and liabilities	(2)	(3)
Purchases	0	0
Settlements	(3)	(5)
Issuances	0	0
Transfers in	0	0
Transfers out	0	0
Fair value based on significant unobservable inputs, ending balance	(4)	(8)
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