Fair Value Measurements (Fair Value of Instruments Recorded at Carrying Amount) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Nuclear Decommissioning Funds Weighted Average Maturity		9 years
Special use funds: nuclear decommissioning fund assets	$ 6,056	$ 6,056	$ 6,003
Special Use Funds Storm Fund Assets	78	78
Available for sale debt securities amortized cost	1,977	$ 1,977	1,921
Available-for-sale Equity Securities, Amortized Cost Basis			1,521
Fair Value Assumptions, Expected Term		1 year
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	825	$ 825	743
Other Investments Financial Instruments Primarily Notes Receivable Fair Value Disclosure	31	31	500
Long Term Debt Including Current Maturities Fair Value Disclosure	29,965	29,965	33,134
Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	826	826	744
Other Investments Financial Instruments Primarily Notes Receivable Fair Value Disclosure	31	31	680
Long Term Debt Including Current Maturities Fair Value Disclosure	31,225	$ 31,225	35,447
FPL [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Nuclear Decommissioning Funds Weighted Average Maturity		9 years
Special use funds: nuclear decommissioning fund assets	4,132	$ 4,132	4,090
Available for sale debt securities amortized cost	1,543	$ 1,543	1,443
Available-for-sale Equity Securities, Amortized Cost Basis			783
Fair Value Assumptions, Expected Term		1 year
FPL [Member] | Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	651	$ 651	593
Long Term Debt Including Current Maturities Fair Value Disclosure	12,471	12,471	11,702
FPL [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	652	652	593
Long Term Debt Including Current Maturities Fair Value Disclosure	13,324	13,324	$ 13,285
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
marketable securities, unrealized gain (loss) on securities still held	78	37
Equity Securities [Member] | FPL [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
marketable securities, unrealized gain (loss) on securities still held	$ 60	$ 37