Employee Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Service cost	$ 18	$ 16
Interest cost	20	21
Expected return on plan assets	(69)	(67)
Amortization of prior service benefit	0	0
Special termination benefits	0	1
Net periodic benefit (income) cost	(31)	(29)
Postretirement Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Service cost	0	0
Interest cost	2	2
Expected return on plan assets	0	0
Amortization of prior service benefit	(4)	0
Special termination benefits	0	0
Net periodic benefit (income) cost	(2)	2
FPL [Member] | Pension Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Net periodic benefit (income) cost	(20)	(18)
FPL [Member] | Postretirement Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Net periodic benefit (income) cost	$ (2)	$ 2