Revenue from Contracts with Customers Revenue from Contracts with Customers - SPPC - Customer Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3,687	$ 3,524
Operating revenue	4,610	4,440
Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	138	155
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,407	3,252
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,156	2,021
Sierra Pacific Power Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	219	222
Sierra Pacific Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	1	2
Sierra Pacific Power Company [Member] | Regulated electric
Disaggregation of Revenue [Line Items]
Operating revenue	182	181
Sierra Pacific Power Company [Member] | Regulated electric | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	1	1
Sierra Pacific Power Company [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Operating revenue	37	41
Sierra Pacific Power Company [Member] | Regulated natural gas | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	0	1
Sierra Pacific Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	218	220
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	17	13
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	181	180
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	17	13
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated natural gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	37	40
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
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	200	206
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	92	94
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	64	68
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	42	42
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	2	2
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	163	166
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	68	68
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	57
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	39	39
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	2	2
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	37	40
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	24	26
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	10	11
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	3	3
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
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
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
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
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	201	207
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	164	167
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	$ 37	$ 40