Income Taxes - Components of Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Federal:
Current	$ 10	$ 0	$ (145)
Deferred	1,194	1,077	853
Total federal	1,204	1,077	708
State:
Current	31	(29)	69
Deferred	(7)	128	0
Total state	24	99	69
Total income taxes	1,228	1,176	777
FPL [Member]
Federal:
Current	423	240	174
Deferred	399	542	540
Total federal	822	782	714
State:
Current	58	68	44
Deferred	77	60	77
Total state	135	128	121
Total income taxes	$ 957	$ 910	$ 835