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Summary of Significant Accounting Policies - MEC - Inventory (Details) - USD ($)
$ in Millions
Dec. 31, 2015
Dec. 31, 2014
Inventory [Line Items]    
Inventory, Raw Materials and Supplies, Gross $ 529 $ 506
Replacement cost of inventory 8 41
MidAmerican Energy Company [Member]    
Inventory [Line Items]    
Inventory, Raw Materials and Supplies, Gross 105 101
Public utility inventory, coal 102 54
Public utility inventory - natural gas in storage 27 24
Replacement cost of inventory $ 8 $ 41