Consolidated Statements of Changes in Equity - SPPC - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Sierra Pacific Power Company [Member]	Sierra Pacific Power Company [Member] Common Stock [Member]	Sierra Pacific Power Company [Member] Additional Paid-in Capital [Member]	Sierra Pacific Power Company [Member] Retained Earnings [Member]	Sierra Pacific Power Company [Member] Accumulated Other Comprehensive (Loss) Income, Net [Member]
Balance (shares) at Dec. 31, 2016		77,000,000					1,000
Stockholders' Equity Attributable to Parent at Dec. 31, 2016						$ 1,108	$ 0	$ 1,111	$ (2)	$ (1)
Net Income (Loss) Attributable to Parent	$ 1,130					41			41
Dividends, Common Stock, Cash						5	0		5	0
Stockholders' Equity, Other	$ 23	$ 0	$ 21	$ (1)	$ 0	(1)	$ 0	0	1
Balance (shares) at Jun. 30, 2017		77,000,000					1,000
Stockholders' Equity Attributable to Parent at Jun. 30, 2017						$ 1,143	$ 0	1,111	33	(1)
Balance (shares) at Dec. 31, 2017	77,000,000	77,000,000				1,000	1,000
Stockholders' Equity Attributable to Parent at Dec. 31, 2017	$ 28,176					$ 1,172	$ 0	1,111	62	(1)
Net Income (Loss) Attributable to Parent	885					41			41
Stockholders' Equity, Other	$ 4		$ 5			$ (1)			1
Balance (shares) at Jun. 30, 2018	77,000,000	77,000,000				1,000	1,000
Stockholders' Equity Attributable to Parent at Jun. 30, 2018	$ 28,175					$ 1,212	$ 0	$ 1,111	$ 102	$ (1)