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Fair Value Measurements - MEC - Debt (Details) - USD ($)
$ in Millions
Sep. 30, 2017
Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, carrying value $ 36,124 $ 36,116
Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, fair value 41,197 40,718
MidAmerican Energy Company [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, carrying value 4,894 4,301
Long-term debt, fair value   $ 4,735
MidAmerican Energy Company [Member] | Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt, fair value $ 5,446