Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value.

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The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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Asset Impairments (Details) - USD ($)		3 Months Ended					12 Months Ended
Asset Impairments (Details) - USD ($)	Sep. 05, 2018	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 20, 2019
Asset Impairments
Impairment losses, other assets							$ 14,000,000	$ 12,000,000
Impairment losses							75,000,000	5,000,000	$ 99,000,000
Equity method investments							346,000,000	388,000,000
Impairment losses on investments							18,000,000	$ 108,000,000	15,000,000
Held-for-sale \| NRG Solar Guam, LLC
Asset Impairments
Impairment losses					$ 12,000,000
Cash consideration										$ 8,000,000
Cottonwood \| West/Other
Asset Impairments
Impairment losses on equity method investments							$ 32,000,000
Home Solar \| West/Other
Asset Impairments
Impairment losses on equity method investments		$ 29,000,000
Petra Nova Parish Holdings
Asset Impairments
Impairment losses on equity method investments				$ 101,000,000
Letter of credit				12,000,000
Contribution in cash				95,000,000
Guarantee (up to)				$ 124,000,000
Ownership percentage							50.00%
Equity method investments							$ (13,000,000)
Petra Nova Parish Holdings \| Texas
Asset Impairments
Impairment losses on equity method investments			$ 18,000,000
Keystone
Asset Impairments
Impairment losses on equity method investments	$ 14,000,000
Ownership percentage	3.70%
Conemaugh
Asset Impairments
Impairment losses on equity method investments	$ 14,000,000
Dunkirk
Asset Impairments
Impairment losses on equity method investments						$ 46,000,000
Equity method investments						$ 0
Other Investments
Asset Impairments
Impairment losses on equity method investments									15,000,000
Impairment losses on investments									$ 13,000,000