Consolidated Statements of Changes in Equity - NPC - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Nevada Power Company [Member]	Nevada Power Company [Member] Common Stock [Member]	Nevada Power Company [Member] Additional Paid-in Capital [Member]	Nevada Power Company [Member] Retained Earnings [Member]	Nevada 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						$ 2,972	$ 0	$ 2,308	$ 667	$ (3)
Net Income (Loss) Attributable to Parent	$ 2,198					263			263
Dividends, Common Stock, Cash						412			412
Stockholders' Equity, Other	$ 24	$ 0	$ 21	$ 0	$ 0
Balance (shares) at Sep. 30, 2017		77,000,000					1,000
Stockholders' Equity Attributable to Parent at Sep. 30, 2017						$ 2,823	$ 0	2,308	518	(3)
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					$ 2,678	$ 0	2,308	374	(4)
Net Income (Loss) Attributable to Parent	2,286					228			228
Stockholders' Equity, Other	$ 5		$ 5			$ 1			1
Balance (shares) at Sep. 30, 2018	77,000,000	77,000,000				1,000	1,000
Stockholders' Equity Attributable to Parent at Sep. 30, 2018	$ 29,557					$ 2,905	$ 0	$ 2,308	$ 601	$ (4)