Employee Benefit Plans - SPPC (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 10
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	9
SPPC | United States | Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	1
SPPC | United States | NV Energy | Other Current Liabilities | Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	(1)	$ (1)
SPPC | United States | NV Energy | Other Noncurrent Liabilities | Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Other long-term liabilities	(8)	(8)
SPPC | United States | NV Energy | Other Noncurrent Liabilities | Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Other long-term liabilities	(13)	(13)
SPPC | Qualified Plan | United States | NV Energy | Other Assets | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Other non-current assets	$ 31	$ 26