Income Taxes - SPPC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of Income Tax Expense (Benefit) [Line Items]
Current Income Tax Expense (Benefit)	$ (591)	$ (573)	$ (687)
Deferred Federal Income Tax Expense (Benefit)	165	(76)	1,164
Other Tax Expense (Benefit)	(6)	(7)	(8)
Income tax (benefit) expense	(583)	(554)	403
Sierra Pacific Power Company [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Current Income Tax Expense (Benefit)	23	0	0
Deferred Federal Income Tax Expense (Benefit)	7	56	50
Unrecognized Tax Benefits, Period Increase (Decrease)	1	0	0
Other Tax Expense (Benefit)	(1)	(1)	(1)
Income tax (benefit) expense	$ 30	$ 55	$ 49