Income Taxes - NPC - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Federal statutory income tax rate	21.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation Regulatory Differences	8.00%	1.00%	0.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	4.00%	31.00%	0.00%
Other, net	(1.00%)	(1.00%)	(2.00%)
Effective income tax rate	(30.00%)	(22.00%)	14.00%
Nevada Power Company [Member]
Income Tax Contingency [Line Items]
Federal statutory income tax rate	21.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Merger Charges, Percent	3.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation Regulatory Differences	0.00%	1.00%	0.00%
Other, net	0.00%	1.00%	(1.00%)
Effective income tax rate	24.00%	38.00%	34.00%
Tax Cuts and Jobs Act of 2017 [Member]
Income Tax Contingency [Line Items]
Federal statutory income tax rate	21.00%
Tax Cuts and Jobs Act of 2017 [Member] \| Nevada Power Company [Member]
Income Tax Contingency [Line Items]
Federal statutory income tax rate	21.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	0.00%	1.00%	0.00%

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

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

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

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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 changes in the income tax rates.

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