Fair Value Measurements (Significant Unobservable Inputs Used in Valuation of Contracts) (Details) - Level 3 [Member] $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($) $ / MWh $ / MMBTU
Forward Contracts - Power [Member] | Discounted Cash Flow Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Forward price (in dollars per energy unit) | $ / MWh	0
Forward Contracts - Power [Member] | Discounted Cash Flow Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Forward price (in dollars per energy unit) | $ / MWh	92
Forward contracts - Gas [Member] | Discounted Cash Flow Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Forward price (in dollars per energy unit) | $ / MMBTU	2
Forward contracts - Gas [Member] | Discounted Cash Flow Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Forward price (in dollars per energy unit) | $ / MMBTU	6
Option Contracts, Power [Member] | Option Models [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Implied volatilities (percent)	8.00%
Implied correlations (percent)	1.00%
Option Contracts, Power [Member] | Option Models [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Implied volatilities (percent)	246.00%
Implied correlations (percent)	100.00%
Option Contracts, Primarily Gas [Member] | Option Models [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Implied volatilities (percent)	0.00%
Implied correlations (percent)	1.00%
Option Contracts, Primarily Gas [Member] | Option Models [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Implied volatilities (percent)	102.00%
Implied correlations (percent)	100.00%
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Forward price (in dollars per energy unit) | $ / MWh	(19.69)
Customer migration rate (percent)	0.00%
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Forward price (in dollars per energy unit) | $ / MWh	230.37
Customer migration rate (percent)	20.00%
Interest Rate Swap [Member] | NextEra Energy Resources [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	$ 117
Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	484
Derivative Financial Instruments, Liabilities [Member] | Forward Contracts - Power [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	216
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Gas [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	11
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Power [Member] | Option Models [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	22
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Primarily Gas [Member] | Option Models [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	208
Derivative Financial Instruments, Liabilities [Member] | Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	27
Derivative Financial Instruments, Assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	1,325
Derivative Financial Instruments, Assets [Member] | Forward Contracts - Power [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	762
Derivative Financial Instruments, Assets [Member] | Forward contracts - Gas [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	24
Derivative Financial Instruments, Assets [Member] | Option Contracts, Power [Member] | Option Models [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	33
Derivative Financial Instruments, Assets [Member] | Option Contracts, Primarily Gas [Member] | Option Models [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	187
Derivative Financial Instruments, Assets [Member] | Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 319