Employee Retirement Benefits - Plan Assets, Benefit Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in plan assets:
Plan assets, beginning balance	$ 3,698
Plan assets, ending balance	3,563	$ 3,698
Pension Benefits [Member]
Change in plan assets:
Plan assets, beginning balance	3,698	3,692
Actual return on plan assets	(8)	203
Benefit payments	(127)	(197)
Plan assets, ending balance	3,563	3,698	$ 3,692
Change in benefit obligation:
Obligation, beginning balance	2,454	2,236
Service cost	70	61	72
Interest cost	97	101	94
Plan amendments	0	(9)
Actuarial losses (gains) - net	(86)	262
Benefit payments	(127)	(197)
Obligation, ending balance	2,408	2,454	$ 2,236
Funded status:
Prepaid (accrued) benefit cost	1,155	1,244
Accumulated benefit obligation	2,366	2,400
Pension Benefits [Member] | FPL [Member]
Funded status:
Prepaid (accrued) benefit cost	$ 1,243	$ 1,189