Revenue from Contract with Customer - SPPC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 15,081	$ 14,837	$ 14,972
Revenues	20,952	19,844	19,787
Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	475	534	601
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13,553	13,433	13,612
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9,421	9,465	9,419
Regulated Operation [Member] | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	619	686	737
Sierra Pacific Power Company [Member]
Disaggregation of Revenue [Line Items]
Revenues	854	889	855
Sierra Pacific Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	5	6	6
Sierra Pacific Power Company [Member] | Electricity US Regulated
Disaggregation of Revenue [Line Items]
Revenues	738	770	752
Sierra Pacific Power Company [Member] | Electricity US Regulated | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	3	4	4
Sierra Pacific Power Company [Member] | Natural Gas US Regulated
Disaggregation of Revenue [Line Items]
Revenues	116	119	103
Sierra Pacific Power Company [Member] | Natural Gas US Regulated | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	2	2	2
Sierra Pacific Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	849	883	849
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	50	57	48
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Electricity US Regulated
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	735	766	748
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Electricity US Regulated | Regulated wholesale, transmission and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	50	57	48
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Natural Gas US Regulated
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	114	117	101
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Natural Gas US Regulated | Regulated wholesale, transmission and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	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	795	822	797
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	681	705	696
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	114	117	101
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	349	344	334
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Residential [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	273	268	267
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Residential [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	76	76	67
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	262	275	271
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Commercial [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	233	245	246
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Commercial [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	29	30	25
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	179	196	185
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Industrial [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	170	186	177
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Industrial [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9	10	8
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	5	7	7
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Other [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5	6	6
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Other [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	1	1
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	4	4	4
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4	4	4
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	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	799	826	801
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Electricity US Regulated | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	685	709	700
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Natural Gas US Regulated | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 114	$ 117	$ 101