Revenue from Contracts with Customers Revenue from Contracts with Customers - NPC - Customer Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3,429	$ 3,564	$ 7,116	$ 7,088
Operating revenue	4,894	4,993	9,504	9,433
Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	138	156	276	311
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,063	3,201	6,470	6,453
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,232	2,311	4,388	4,332
Nevada Power Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	527	562	922	957
Nevada Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	7	6	13	11
Nevada Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	520	556	909	946
Nevada Power Company [Member] | Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	506	543	878	923
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	14	13	31	23
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	498	535	863	908
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	266	312	466	505
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	114	110	204	205
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	112	108	182	187
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	6	5	11	11
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	$ 8	$ 15	$ 15