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Subsidiary Debt Subsidiary Debt - MEC - Maturity Schedule (Details)
$ in Millions
Dec. 31, 2017
USD ($)
Debt Instrument [Line Items]  
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months $ 3,431
Long-term Debt, Maturities, Repayments of Principal in Year Two 2,103
Long-term Debt, Maturities, Repayments of Principal in Year Three 1,674
Long-term Debt, Maturities, Repayments of Principal in Year Four 886
Long-term Debt, Maturities, Repayments of Principal in Year Five 1,838
Long-term Debt, Maturities, Repayments of Principal after Year Five 25,444
MidAmerican Energy Company [Member]  
Debt Instrument [Line Items]  
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 350
Long-term Debt, Maturities, Repayments of Principal in Year Two 501
Long-term Debt, Maturities, Repayments of Principal in Year Three 2
Long-term Debt, Maturities, Repayments of Principal in Year Four 0
Long-term Debt, Maturities, Repayments of Principal in Year Five 0
Long-term Debt, Maturities, Repayments of Principal after Year Five $ 4,227