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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 4,213	$ 4,270	$ 11,329	$ 11,358
Operating revenue	5,644	5,637	15,148	15,070
Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	124	149	400	460
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,753	3,844	10,223	10,297
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,968	2,971	7,356	7,303
Nevada Power Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	806	820	1,728	1,777
Nevada Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	6	6	19	17
Nevada Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	800	814	1,709	1,760
Nevada Power Company [Member] | Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	792	799	1,670	1,722
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	8	15	39	38
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	783	790	1,646	1,698
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	468	484	934	989
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	142	135	346	340
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	169	164	351	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	4	7	15	18
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	$ 9	$ 9	$ 24	$ 24