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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Income Taxes Income Taxes - NPC (Details)	3 Months Ended		12 Months Ended
Income Taxes Income Taxes - NPC (Details)	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Effective Income Tax Rate Reconciliation [Line Items]
Federal statutory income tax rate	21.00%	35.00%	35.00%
Tax Cuts and Jobs Act of 2017 [Member]
Schedule of Effective Income Tax Rate Reconciliation [Line Items]
Federal statutory income tax rate	21.00%
Nevada Power Company [Member]
Schedule of Effective Income Tax Rate Reconciliation [Line Items]
Federal statutory income tax rate		35.00%
Nevada Power Company [Member] \| Tax Cuts and Jobs Act of 2017 [Member]
Schedule of Effective Income Tax Rate Reconciliation [Line Items]
Federal statutory income tax rate	21.00%