Income Taxes (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Jan. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective income tax rate (as a percent)		12.00%		30.00%	23.00%	29.00%
Production tax credits		$ 19		$ 27	$ 63	$ 85
Deferred income tax benefit associated with convertible investment tax credits		$ 34		$ 51	$ 104	$ 220
Tax Cuts and Jobs Act of 2017, income tax expense (benefit)			$ 125
Production tax credit (PTC), roll off period					10 years
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax liability, income tax (expense) benefit							$ 6,500
FPL [Member]
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax liability, income tax (expense) benefit							4,500
NextEra Energy Resources [Member]
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax liability, income tax (expense) benefit							$ 2,000
Accounting Standards Update 2018-02 [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
Income Tax Contingency [Line Items]
Cumulative effect on retained earnings, after tax	$ 16