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Investments Accounted for by the Equity Method and Variable Interest Entities - Summary of Equity Method Investments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investments Accounted for by the Equity Method
Equity investments in affiliates	$ 1,038	$ 1,120
Undistributed earnings by equity investment	$ 120	$ 101
GenConn
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ 102
Gladstone Power Station
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	37.50%
Equity investments in affiliates	$ 139
United States | Avenal Solar Holdings LLC
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ (6)
United States | Desert Sunlight
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	25.00%
Equity investments in affiliates	$ 272
United States | Elkhorn Ridge Wind, LLC
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	47.00%
Equity investments in affiliates	$ 73
United States | GenConn
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ 102
United States | Four Brothers Holdings
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ 213
United States | Granite Mountain Renewables
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ 78
United States | Iron Springs Renewables
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ 54
United States | Midway-Sunset Cogeneration Company
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	50.00%
Equity investments in affiliates	$ 16
United States | San Juan Mesa Wind Project, LLC
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	75.00%
Equity investments in affiliates	$ 66
United States | Watson Cogeneration Company
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	49.00%
Equity investments in affiliates	$ 21
United States | Various
Investments Accounted for by the Equity Method
Equity investments in affiliates	$ 10
Australia | Gladstone Power Station
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)	37.50%
Equity investments in affiliates	$ 139
Mechanically-complete Solar Assets | Sun Edison Utility-Scale Solar and Wind
Investments Accounted for by the Equity Method
Equity investments in affiliates	$ 345

X

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
-Paragraph 1
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- Definition

Amount of consolidated retained earnings that represent undistributed (not yet received) earnings from 50% or less owned persons accounted for by the equity method (equity method investees).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 20
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6462270&loc=d3e57205-112772

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