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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	$ 722		$ 722		$ 665
Revenue from Contract with Customer, Excluding Assessed Tax	3,564		7,088
Revenues	4,993	$ 4,554	9,433	$ 8,720
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,201		6,453
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,311		4,332
Regulated Operation [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	101		226
Sierra Pacific Power Company [Member]
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	53		53		$ 62
Revenues	188	$ 177	410	$ 370
Sierra Pacific Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2		4
Sierra Pacific Power Company [Member] | Electric Operations [Member]
Disaggregation of Revenue [Line Items]
Revenues	169		350
Sierra Pacific Power Company [Member] | Electric Operations [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2		3
Sierra Pacific Power Company [Member] | Natural Gas Operations [Member]
Disaggregation of Revenue [Line Items]
Revenues	19		60
Sierra Pacific Power Company [Member] | Natural Gas Operations [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	0		1
Sierra Pacific Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	186		406
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	10		23
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Electric Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	167		347
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	10		23
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	19		59
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		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	175		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		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	62		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	40		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		3
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	156		322
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	59		127
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	58		115
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	38		77
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	1		3
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	19		59
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	13		39
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	4		15
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	2		5
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		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		2
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		2
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		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	176		383
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	157		324
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	$ 19		$ 59