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Borrowings and Other Financing Instruments Forward Equity Agreement (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from issuance of common stock	$ 13	$ 5
Dividend Reinvestment Program
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from issuance of common stock	$ 38	$ 30

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

+ Details

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Period Type:	duration

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- Details

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Namespace Prefix:
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Period Type: