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Risk Management and Hedging Activities (MEC) Collateral and Contingent Features (Details) (MidAmerican Energy Company [Member], Commodity Contract [Member], USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
MidAmerican Energy Company [Member] | Commodity Contract [Member]
   
Derivative [Line Items]    
Derivatives, net liability positions with specific credit-risk features, aggregate fair value $ 36 $ 84
Collateral already posted, aggregate fair value 0 0
Additional dollateral, aggregate fair value $ 18 $ 72