Employee Retirement Benefits - Net Periodic Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets, Net of Management Fees	7.35%	7.35%
Net periodic benefit (income) cost [Abstract]
Service cost	$ 62	$ 70	$ 61
Interest cost	105	97	101
Expected return on plan assets	(260)	(253)	(241)
Amortization of prior service cost (benefit)	1	1	5
Amortization of losses	0	0	0
Net periodic (income) cost	(92)	(85)	(74)
Other Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Service cost	2	3	3
Interest cost	13	13	16
Expected return on plan assets	(1)	(1)	(1)
Amortization of prior service cost (benefit)	(2)	(3)	(3)
Amortization of losses	0	2	0
Net periodic (income) cost	12	14	15
FPL [Member] | Pension Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Net periodic (income) cost	(58)	(55)	(47)
FPL [Member] | Other Benefits [Member]
Net periodic benefit (income) cost [Abstract]
Net periodic (income) cost	$ 9	$ 11	$ 11