Condensed Financial Statements - Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Tax Equity Contributions	$ 698	$ 403	$ 584
Parent Company [Member]
Debt Instrument [Line Items]
Guarantor obligations, related party disclosure	297
Tax Equity Contributions	$ 1,383

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant