Income Taxes - NPC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of Income Tax Expense (Benefit) [Line Items]
Current federal tax expense (benefit)	$ (888)	$ (591)	$ (573)
Deferred Federal Income Tax Expense (Benefit)	431	165	(76)
Other Tax Expense (Benefit)	(6)	(6)	(7)
Income tax benefit	(598)	(583)	(554)
Nevada Power Company [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Current federal tax expense (benefit)	105	84	62
Deferred Federal Income Tax Expense (Benefit)	(31)	(13)	95
Unrecognized Tax Benefits, Period Increase (Decrease)	0	2	0
Other Tax Expense (Benefit)	(1)	(1)	(1)
Income tax benefit	$ 73	$ 72	$ 156