Income Taxes - SPPC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of Income Tax Expense (Benefit) [Line Items]
Current federal tax expense (benefit)	$ (687)	$ (816)	$ (1,746)
Deferred Federal Income Tax Expense (Benefit)	1,164	1,310	2,296
Deferred State and Local Income Tax Expense (Benefit)	(59)	(53)	37
Deferred Income Tax Expense (Benefit)	1,098	1,274	2,344
Other Tax Expense (Benefit)	(8)	(8)	(9)
Income tax expense	403	450	589
Sierra Pacific Power Company [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Deferred Federal Income Tax Expense (Benefit)	50	48	48
Other Tax Expense (Benefit)	(1)	(1)	(1)
Income tax expense	$ 49	$ 47	$ 47