Revenue - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)
Regulatory Liabilities [Line Items]
Revenue recognized related to rate case settlement	$ 17
Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Liability held in reserve to be refunded to customer	$ 21

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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