Income Taxes - NPC - Components of Net Deferred Income Tax Liability (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets and Liabilities [Line Items]
Employee benefits	$ 190	$ 187
Regulatory liabilities	834	812
Other	815	781
Total deferred income tax assets	3,104	2,872
Valuation allowances	(35)	(23)
Total deferred income tax assets, net	3,069	2,849
Property-related items	(13,157)	(11,989)
Regulatory assets	(1,446)	(1,374)
Other	(299)	(301)
Total deferred income tax liabilities	(15,754)	(14,363)
Deferred Tax Liabilities, Net	12,685	11,514
MidAmerican Funding, LLC and Subsidiaries [Domain]
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	327	332
Other	68	70
Total deferred income tax assets, net	704	685
Property-related items	(3,326)	(2,950)
Regulatory assets	(418)	(366)
Other	(16)	(25)
Total deferred income tax liabilities	(3,760)	(3,341)
Deferred Tax Liabilities, Net	3,056	2,656
Nevada Power Company [Member]
Deferred Tax Assets and Liabilities [Line Items]
Deferred Tax Assets, Operating Loss and Credit Carryforwards, Federal	15	158
Deferred Tax Assets, Tax Deferred Expense, Leases	174	178
Employee benefits	30	22
Regulatory liabilities	47	37
Other	39	57
Total deferred income tax assets	305	452
Valuation allowances	(5)	(2)
Total deferred income tax assets, net	300	450
Property-related items	(1,242)	(1,175)
Regulatory assets	(275)	(341)
Deferred Tax Liabilities, Tax Deferred Expense, Leases	(169)	(174)
Other	(19)	(29)
Total deferred income tax liabilities	(1,705)	(1,719)
Deferred Tax Liabilities, Net	$ 1,405	$ 1,269