Revenue from Contracts with Customers Revenue from Contracts with Customers - SPPC - 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
Sierra Pacific Power Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	194	188	413	410
Sierra Pacific Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	2	2	3	4
Sierra Pacific Power Company [Member] | Regulated electric
Disaggregation of Revenue [Line Items]
Operating revenue	172	169	354	350
Sierra Pacific Power Company [Member] | Regulated electric | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	1	2	2	3
Sierra Pacific Power Company [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Operating revenue	22	19	59	60
Sierra Pacific Power Company [Member] | Regulated natural gas | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	1	0	1	1
Sierra Pacific Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	192	186	410	406
Sierra Pacific 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	11	10	28	23
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	171	167	352	347
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated electric | Regulated wholesale, transmission and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11	10	28	23
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21	19	58	59
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated natural gas | Regulated wholesale, transmission and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	180	175	380	381
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	72	72	164	166
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	59	62	123	130
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	48	40	90	82
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1	1	3	3
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated electric | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	159	156	322	322
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated electric | Regulated retail electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	58	59	126	127
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated electric | Regulated retail electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	54	58	108	115
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated electric | Regulated retail electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	46	38	85	77
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated electric | Regulated retail electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1	1	3	3
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21	19	58	59
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated natural gas | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	14	13	38	39
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated natural gas | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5	4	15	15
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated natural gas | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2	2	5	5
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated natural gas | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1	1	2	2
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Regulated electric | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1	1	2	2
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	181	176	382	383
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Regulated electric | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	160	157	324	324
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 21	$ 19	$ 58	$ 59