Revenue from Contracts with Customers Revenue from Contracts with Customers - NPC - Customer Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 4,357	$ 4,213	$ 11,190	$ 11,329
Operating revenue	6,193	5,644	15,332	15,148
Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	94	124	314	400
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,927	3,753	10,109	10,223
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,981	2,968	7,214	7,356
Nevada Power Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	808	806	1,706	1,728
Nevada Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	7	6	20	19
Nevada Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	801	800	1,686	1,709
Nevada Power Company [Member] | Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	780	792	1,638	1,670
Nevada Power Company [Member] | Regulated Operation [Member] | Regulated wholesale, transmission and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21	8	48	39
Nevada Power Company [Member] | Fully bundled customer [Member] | Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	772	783	1,618	1,646
Nevada Power Company [Member] | Fully bundled customer [Member] | Regulated Operation [Member] | Regulated retail electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	495	468	993	934
Nevada Power Company [Member] | Fully bundled customer [Member] | Regulated Operation [Member] | Regulated retail electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	127	142	317	346
Nevada Power Company [Member] | Fully bundled customer [Member] | Regulated Operation [Member] | Regulated retail electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	147	169	300	351
Nevada Power Company [Member] | Fully bundled customer [Member] | Regulated Operation [Member] | Regulated retail electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3	4	8	15
Nevada Power Company [Member] | Distribution only service [Member] | Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 8	$ 9	$ 20	$ 24