Revenue from Contracts with Customers Revenue from Contracts with Customers - SPPC - Customer Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 4,357	$ 4,213	$ 11,190	$ 11,329
Operating revenue	6,193	5,644	15,332	15,148
Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	94	124	314	400
Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,927	3,753	10,109	10,223
Regulated Operation [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,981	2,968	7,214	7,356
Regulated Operation [Member] | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	84	77	422	490
Sierra Pacific Power Company [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	235	248	652	661
Sierra Pacific Power Company [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	1	1	4	4
Sierra Pacific Power Company [Member] | Regulated Electric [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	220	232	569	586
Sierra Pacific Power Company [Member] | Regulated Electric [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	1	0	3	2
Sierra Pacific Power Company [Member] | Regulated Gas [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	15	16	83	75
Sierra Pacific Power Company [Member] | Regulated Gas [Member] | Non-contracts with customer revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenue	0	1	1	2
Sierra Pacific Power Company [Member] | Regulated Operation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	234	247	648	657
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	13	16	37	44
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	219	232	566	584
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated Electric [Member] | Regulated wholesale, transmission and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13	16	37	44
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	15	15	82	73
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Regulated Gas [Member] | 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	220	230	608	610
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	87	86	262	250
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	74	83	203	206
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	58	59	140	149
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	2	3	5
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Electric [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	205	215	526	537
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Electric [Member] | Regulated retail electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	76	75	208	201
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Electric [Member] | Regulated retail electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	71	80	183	188
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Electric [Member] | Regulated retail electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	57	58	132	143
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Electric [Member] | Regulated retail electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1	2	3	5
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Gas [Member] | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	15	15	82	73
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Gas [Member] | Regulated retail gas [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11	11	54	49
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Gas [Member] | Regulated retail gas [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3	3	20	18
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Gas [Member] | Regulated retail gas [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1	1	8	6
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled customer [Member] | Regulated Gas [Member] | Regulated retail gas [Member] | 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	3	3
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Distribution only service [Member] | Regulated Electric [Member] | Regulated retail electric [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] | Distribution only service [Member] | Regulated Gas [Member] | Regulated retail gas [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 and distribution services only customer [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	221	231	611	613
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Regulated Electric [Member] | Regulated retail electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	206	216	529	540
Sierra Pacific Power Company [Member] | Regulated Operation [Member] | Fully bundled and distribution services only customer [Member] | Regulated Gas [Member] | Regulated retail gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 15	$ 15	$ 82	$ 73