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Investments and Restricted Cash and Investments Investments and Restricted Cash and Investments - MEC - (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Investments and restricted cash and investments $ 4,872 $ 3,945
MidAmerican Energy Company [Member]    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Decommissioning Fund Investments, Fair Value 515 460
Life Insurance, Corporate or Bank Owned, Amount 198 184
Other Investments 15 9
Investments and restricted cash and investments $ 728 $ 653
MidAmerican Energy Company [Member] | Domestic Equity Securities [Member]    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Nuclear Decommissioning Trust Fund Ownership Percentage 56.00% 54.00%
MidAmerican Energy Company [Member] | US Government Corporations and Agencies Securities [Member]    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Nuclear Decommissioning Trust Fund Ownership Percentage 34.00% 35.00%
MidAmerican Energy Company [Member] | Domestic Corporate Debt Securities [Member]    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Nuclear Decommissioning Trust Fund Ownership Percentage 7.00% 8.00%
MidAmerican Energy Company [Member] | Other Securities [Member]    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Nuclear Decommissioning Trust Fund Ownership Percentage 3.00% 3.00%