Employee Benefit Plans - NPC (Details) - NPC - United States - NV Energy - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Other Assets | Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Other non-current assets	$ 4	$ 4
Other Current Liabilities | Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	(1)	(1)
Other Noncurrent Liabilities | Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Other long-term liabilities	(9)	(9)
Qualified Plan | Other Assets | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Other non-current assets	$ 10	$ 8