Fair Value Measurements (Reconciliation of Change in Fair Value of Derivatives, Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Financial Instruments, Net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of net derivatives based on significant unobservable inputs at December 31 of prior year	$ 647	$ 566	$ 578
Realized and unrealized gains (losses):
Included in earnings	923	35	376
Included in other comprehensive income (loss)	5	7	(18)
Included in regulatory assets and liabilities	1	(18)	0
Purchases	141	152	126
Settlements	(356)	28	(317)
Issuances	(87)	(115)	(197)
Impact of adoption of new revenue standard	0	(30)	0
Transfers in	(5)	0	17
Transfers out	(62)	22	1
Fair value of net derivatives based on significant unobservable inputs at December 31	1,207	647	566
Gains (losses) included in earnings attributable to the change in unrealized gains (losses) relating to derivatives held at the reporting date	611	100	277
Realized and unrealized gains (losses) reflected in operating revenues	956	48	379
Unrealized gains (losses) reflected in operating revenues, for derivatives still held at the reporting date	638	112	281
FPL[Member] | Derivative Financial Instruments, Net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of net derivatives based on significant unobservable inputs at December 31 of prior year	(36)	0	1
Realized and unrealized gains (losses):
Included in earnings	0	(1)	0
Included in other comprehensive income (loss)	0	0	0
Included in regulatory assets and liabilities	1	(18)	0
Purchases	0	(16)	0
Settlements	25	(2)	(1)
Issuances	0	0	0
Impact of adoption of new revenue standard	0	0
Transfers in	0	0	0
Transfers out	2	1	0
Fair value of net derivatives based on significant unobservable inputs at December 31	(8)	(36)	0
Gains (losses) included in earnings attributable to the change in unrealized gains (losses) relating to derivatives held at the reporting date	0	$ (1)	$ 0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, Fair Value Disclosure	390
Interest Rate Swap [Member] | Significant Unobservable Inputs (Level 3) [Member] | NEER [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, Fair Value Disclosure	$ 133