Summary of Significant Accounting Policies - NPC - Segment Information (Details)	12 Months Ended
Dec. 31, 2020 TheNumberOfReportableSegments OperatingSegments
Segment Reporting Information [Line Items]
Number of Reportable Segments \| OperatingSegments	8
Nevada Power Company [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments \| TheNumberOfReportableSegments	1

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

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