Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) MW
Accounting Policies [Abstract]
Sale of noncontrolling interest	$ 428
Plant capacity sold (in MW) \| MW	718
Allocation of losses to noncontrolling tax equity members	$ 165

Amount of increase in noncontrolling interest from subsidiary issuance of equity interests to noncontrolling interest holders.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Reference 2: 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 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration