Income Taxes - Narrative (Details) $ in Billions	12 Months Ended
	Dec. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax liability, income tax expense (benefit)	$ 6.5
FPL[Member]
Operating Loss Carryforwards [Line Items]
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax liability, income tax expense (benefit)	4.5
NEER [Member]
Operating Loss Carryforwards [Line Items]
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax liability, income tax expense (benefit)	$ 2.0