Summary of Significant Accounting Policies - Noncontrolling Interest (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Noncontrolling Interest [Roll Forward]
Balance as of beginning of period	$ 2,314
Dividends paid to NRG Yield, Inc. public shareholders	(61)
Distributions to noncontrolling interest	(43)
Net income attributable to noncontrolling interest - continuing operations	5
Net income attributable to noncontrolling interest - discontinued operations	21
Other comprehensive income attributable to noncontrolling interest - discontinued operations	14
Contributions from noncontrolling interest	296
Sale of assets to NRG Yield, Inc.	(8)
Balance as of end of period	0
Noncontrolling Interest
Noncontrolling Interest [Roll Forward]
Non-cash adjustments to noncontrolling interest	10
Agua Caliente
Noncontrolling Interest [Roll Forward]
Deconsolidation	(279)
NRG Yield and Renewables
Noncontrolling Interest [Roll Forward]
Deconsolidation	(2,180)
Ivampah
Noncontrolling Interest [Roll Forward]
Deconsolidation	$ (89)

Noncontrolling interest, Contributions from Noncontrolling Interests

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Amount after tax of income (loss) from continuing operations attributable to the noncontrolling interest.

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Amount after tax of income (loss) from a discontinued operation attributable to the noncontrolling interest. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders.

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The amount of the reduction or elimination during the period of a noncontrolling interest resulting from the parent's loss of control and deconsolidation of the entity in which one or more outside parties had a noncontrolling interest.

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