Revenue from Contracts with Customers Revenue from Contracts with Customers - SPPC - Customer Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	$ 582		$ 665
Revenue from Contract with Customer, Excluding Assessed Tax	3,524
Revenues	4,440	$ 4,166
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,252
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,021
Regulated Operation [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	125
Sierra Pacific Power Company [Member]
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	57		62
Revenues	222	$ 193
Sierra Pacific Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2
Sierra Pacific Power Company [Member] | Electric Operations [Member]
Disaggregation of Revenue [Line Items]
Revenues	181
Sierra Pacific Power Company [Member] | Electric Operations [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	1
Sierra Pacific Power Company [Member] | Natural Gas Operations [Member]
Disaggregation of Revenue [Line Items]
Revenues	41
Sierra Pacific Power Company [Member] | Natural Gas Operations [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	1
Sierra Pacific Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	220
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Electric Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	180
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Electric Operations [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Natural Gas Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	40
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Natural Gas Operations [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	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	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	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	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
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
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Electric Operations [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	166
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Electric Operations [Member] | Regulated retail electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	68
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Electric Operations [Member] | Regulated retail electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	57
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Electric Operations [Member] | Regulated retail electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	39
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Electric Operations [Member] | Regulated retail electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Natural Gas Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	40
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Natural Gas Operations [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	26
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Natural Gas Operations [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Natural Gas Operations [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Natural Gas Operations [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	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
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Electric Operations [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Natural Gas Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	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	207
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Electric Operations [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	167
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Natural Gas Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	40
Nevada Power Company [Member]
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	97		$ 111
Revenues	395
Nevada Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	5
Nevada Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	390
Nevada Power Company [Member] | Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	380
Nevada Power Company [Member] | Regulated Operation [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	10
Nevada Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	373
Nevada Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated retail electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	193
Nevada Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated retail electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	95
Nevada Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated retail electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	79
Nevada Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated retail electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6
Nevada Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 7