Employee Retirement Benefits - Net Periodic Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Service cost	$ 85	$ 80	$ 70
Interest cost	92	114	82
Expected return on plan assets	(321)	(312)	(276)
Amortization of actuarial loss	18	0	0
Amortization of prior service benefit	(1)	(1)	(1)
Special termination benefits	16	19	35
Net periodic (income) cost	(111)	(100)	(90)
Other Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Service cost	1	1	1
Interest cost	8	9	7
Expected return on plan assets	0	0	0
Amortization of actuarial loss	3	0	0
Amortization of prior service benefit	(16)	(15)	(15)
Special termination benefits	0	0	0
Net periodic (income) cost	(4)	(5)	(7)
FPL[Member] | Pension Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Net periodic (income) cost	(77)	(71)	(57)
FPL[Member] | Other Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Net periodic (income) cost	$ (3)	$ (4)	$ (6)