Fair Value Measurements (Fair Value of Instruments Recorded at Other than Fair Value) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Decommissioning Fund Investments, Fair Value	$ 6,003	$ 5,434
Available for sale debt securities amortized cost	1,921	1,820
Available-for-sale equity securities, amortized cost	$ 1,521	1,543
Special Use Funds Nuclear Decommissioning Funds Weighted Average Maturity	9 years
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	$ 743	712
Other Investments Primarily Notes Receivable Fair Value Disclosure	500	526
Long Term Debt Including Current Maturities Fair Value Disclosure	33,134	30,418
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	744	712
Other Investments Primarily Notes Receivable Fair Value Disclosure	680	668
Long Term Debt Including Current Maturities Fair Value Disclosure	35,447	31,623
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long Term Debt Including Current Maturities Fair Value Disclosure	33,743	29,804
liabilities associated with assets held-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	373	373
FPL[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	11,702	10,072
Special Use Funds Storm Fund Assets	0	0
Decommissioning Fund Investments, Fair Value	4,090	3,665
Available for sale debt securities amortized cost	1,443	1,373
Available-for-sale equity securities, amortized cost	$ 783	764
Special Use Funds Nuclear Decommissioning Funds Weighted Average Maturity	9 years
FPL[Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	$ 593	557
Long Term Debt Including Current Maturities Fair Value Disclosure	11,702	10,072
FPL[Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Special Use Funds Fair Value Disclosure	593	557
Long Term Debt Including Current Maturities Fair Value Disclosure	$ 13,285	$ 11,211