Income Taxes - NPC - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Federal statutory income tax rate	21.00%	21.00%	21.00%	35.00%
Effective Income Tax Rate Reconciliation Regulatory Differences	3.00%	6.00%	8.00%
Other, net	(1.00%)	(1.00%)	(1.00%)
Effective income tax rate	4.00%	(25.00%)	(30.00%)
Nevada Power Company [Member]
Income Tax Contingency [Line Items]
Federal statutory income tax rate	21.00%	21.00%	21.00%
Effective Income Tax Rate Reconciliation Regulatory Differences	(8.00%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Merger Charges, Percent	0.00%	0.00%	3.00%
Other, net	1.00%	1.00%	0.00%
Effective income tax rate	14.00%	22.00%	24.00%

Effective Income Tax Rate Reconciliation, Nondeductible Expense, Merger Charges, Percent

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- Definition

The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate that can be explained by the tax effect of certain temporary differences due to state utility rate regulation.

+ References

No definition available.

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- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

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- 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.

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