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Income Taxes - MEC (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]          
Federal statutory income tax rate 21.00% 35.00% 21.00% 35.00% 35.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent (78.00%) (19.00%) (58.00%) (17.00%)  
State income tax, net of federal income tax benefit 19.00% (1.00%) 25.00% 2.00%  
Effects of ratemaking (8.00%) (0.00%) (8.00%) (0.00%)  
Other, net 1.00% (0.00%) (1.00%) (1.00%)  
Effective income tax rate 86.00% (13.00%) 81.00% (11.00%)  
Production Tax Credit Carryforwards [Abstract]          
Years eligible for federal renewable energy production tax credit     10 years    
Related Party Income Tax Receivable (Payable) [Abstract]          
Related party transaction, cash received for income taxes, net     $ 311    
Tax Cuts and Jobs Act of 2017 [Member]          
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]          
Federal statutory income tax rate     21.00%    
Iowa Senate File 2417, Rate Effective Starting 2021 [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Deferred Tax Liabilities, Net $ 61   $ 61    
Deferred Income Tax Expense (Benefit)     $ 2    
MidAmerican Energy Company [Member]          
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]          
Federal statutory income tax rate 21.00% 35.00% 21.00% 35.00% 35.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent (80.00%) (67.00%) (104.00%) (73.00%)  
State income tax, net of federal income tax benefit (7.00%) (4.00%) (8.00%) (2.00%)  
Effects of ratemaking (9.00%) (5.00%) (13.00%) (7.00%)  
Other, net (2.00%) (0.00%) (0.00%) (0.00%)  
Effective income tax rate (77.00%) (41.00%) (104.00%) (47.00%)  
Production Tax Credit Carryforwards [Abstract]          
Years eligible for federal renewable energy production tax credit     10 years    
MidAmerican Energy Company [Member] | Berkshire Hathaway Energy [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Related party transaction, cash received for income taxes, net     $ 228 $ 7  
MidAmerican Energy Company [Member] | Tax Cuts and Jobs Act of 2017 [Member]          
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]          
Federal statutory income tax rate     21.00%    
MidAmerican Energy Company [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Deferred Tax Liabilities, Net $ 54   $ 54    
Deferred Income Tax Expense (Benefit)     $ 2    
Maximum [Member] | IOWA | Tax Year, Current [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Statutory Income Tax Rate, State and Local, Percent     12.00%    
Maximum [Member] | IOWA | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Statutory Income Tax Rate, State and Local, Percent     9.80%    
Deferred Income Taxes [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Regulatory Liabilities 59   $ 59    
Deferred Income Taxes [Member] | MidAmerican Energy Company [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]          
Related Party Income Tax Receivable (Payable) [Abstract]          
Regulatory Liabilities $ 56   $ 56