Consolidated Entities and Equity Method Investments - Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Noncontrolling Interest [Roll Forward]
Redemption of redeemable noncontrolling interests		$ (129)
Southern Power
Noncontrolling Interest [Roll Forward]
Beginning balance	$ 164	43
Net income attributable to redeemable noncontrolling interests	2	4
Distributions to redeemable noncontrolling interests	(2)	(1)
Capital contributions from redeemable noncontrolling interests	2	118
Redemption of redeemable noncontrolling interests	(59)	(129)
Reclassification to non-redeemable noncontrolling interests	(114)
Change in fair value of redeemable noncontrolling interests	7
Ending balance	$ 0	$ 164

Capital Contributions From Redeemable Noncontrolling Interest

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- Definition

Distributions To Redeemable Noncontrolling Interest

+ References

No definition available.

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- Definition

Redeemable Noncontrolling Interest, Equity, Fair Value Increase (Decrease)

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No definition available.

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- Definition

Redeemable Noncontrolling Interest, Reclassification to Noncontrolling Interests

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- Definition

Redeemable put option.

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No definition available.

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- Definition

Decrease in noncontrolling interest (for example, but not limited to, redeeming or purchasing the interests of noncontrolling shareholders, issuance of shares (interests) by the non-wholly owned subsidiary to the parent entity for other than cash, and a buyback of shares (interest) by the non-wholly owned subsidiary from the noncontrolling interests).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569655-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4616395-111683

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.19)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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