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