Employee Retirement Benefits - Plan Assets, Benefit Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in pension plan assets:
Plan assets, beginning balance	$ 4,020
Plan assets, ending balance	3,806	$ 4,020
Pension Benefits [Member]
Change in pension plan assets:
Plan assets, beginning balance	4,020	3,651
Actual return on plan assets	(69)	574
Benefit payments	(160)	(205)
Acquisitions	15	0
Plan assets, ending balance	3,806	4,020	$ 3,651
Change in pension benefit obligation:
Obligation, beginning balance	2,593	2,474
Service cost	70	66	62
Interest cost	82	83	105
Acquisitions	15	0
Special termination benefits	35	38	0
Plan amendments	0	12
Actuarial losses (gains) - net	(113)	125
Benefit payments	(160)	(205)
Obligation, ending balance	2,522	2,593	$ 2,474
Funded status:
Prepaid (accrued) benefit cost	1,284	1,427
Accumulated benefit obligation	2,479	2,548
FPL[Member] | Pension Benefits [Member]
Funded status:
Prepaid (accrued) benefit cost	$ 1,407	$ 1,351