Income Taxes - Components of Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Federal:
Current	$ 72	$ 10	$ 0
Deferred	1,075	1,194	1,077
Total federal	1,147	1,204	1,077
State:
Current	76	31	(29)
Deferred	160	(7)	128
Total state	236	24	99
Total income taxes	1,383	1,228	1,176
FPL [Member]
Federal:
Current	72	423	240
Deferred	830	399	542
Total federal	902	822	782
State:
Current	57	58	68
Deferred	92	77	60
Total state	149	135	128
Total income taxes	$ 1,051	$ 957	$ 910