Short-Term Debt and Credit Facilities - NPC - Credit Facility (Details)		Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]	$ 11,030,000,000	$ 9,412,000,000
Short-term debt	[1]	$ 2,286,000,000	3,214,000,000
Nevada Power Company [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt To Capitalization Ratio		0.65
Nevada Power Company [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Short-term debt		$ 0	$ 0
Nevada Power Company [Member] | Secured credit facility, $400 million, expiring June 2022 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 400,000,000
Nevada Power Company [Member] | Minimum [Member] | Secured credit facility, $400 million, expiring June 2022 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt To Capitalization Ratio		0.65

[1] The table does not include unused credit facilities and letters of credit for investments that are accounted for under the equity method.