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Income Taxes (LLC) Reconciliation of Effective Income Tax Rate (Details) (MidAmerican Funding, LLC and Subsidiaries [Domain], USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]          
Federal statutory income tax rate     35.00% 35.00% 35.00%
Income tax credits     (60.00%) (34.00%) (30.00%)
State income tax, net of federal income tax benefit     (12.00%) (1.00%) (4.00%)
Income tax method changes     (6.00%) (11.00%) (19.00%)
Effects of ratemaking     (1.00%) 0.00% (3.00%)
Other, net     (2.00%) 2.00% (1.00%)
Effective federal and state income tax rate     (46.00%) (9.00%) (22.00%)
Production Tax Credit Carryforwards [Abstract]          
Years eligible for renewable energy production tax credit     10 years    
Income tax method change [Abstract]          
Income tax benefits from tax method change $ 18 $ 35      
Repairs deduction [Member]
         
Income tax method change [Abstract]          
Income tax benefits from tax method change     16   17
A&G deduction [Member]
         
Income tax method change [Abstract]          
Income tax benefits from tax method change         44
Tax method changes, issue resolutions [Member]
         
Income tax method change [Abstract]          
Income tax benefits from tax method change       35