Revenue from Contract with Customer - NPC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 25,150	$ 20,952	$ 19,844
Regulated assets | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	9,801	9,421	9,465
NPC
Disaggregation of Revenue [Line Items]
Other revenue	22	26	25
Total operating revenue	2,139	1,998	2,148
NPC | Regulated assets
Disaggregation of Revenue [Line Items]
Customer revenue	2,117	1,972	2,123
NPC | Regulated assets | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Customer revenue	74	62	57
NPC | Regulated assets | Fully bundled | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	2,021	1,886	2,035
NPC | Regulated assets | Fully bundled | Residential | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	1,207	1,145	1,141
NPC | Regulated assets | Fully bundled | Commercial | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	414	384	441
NPC | Regulated assets | Fully bundled | Industrial | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	386	345	433
NPC | Regulated assets | Fully bundled | Other retail | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	14	12	20
NPC | Regulated assets | Distribution only service | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	22	24	31
NPC | Regulated assets | Fully bundled and distribution services only customer | Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	$ 2,043	$ 1,910	$ 2,066