Summary of Significant Accounting Policies Summary of Significant Accounting Policies - MEC - New Accounting Pronouncements (Details) $ in Millions	Dec. 31, 2014 USD ($)
Other Current Assets [Member] | Accounting Standards Update 2015-17 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 291
Other Current Assets [Member] | MidAmerican Energy Company [Member] | Accounting Standards Update 2015-17 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	1
Deferred Income Taxes [Member] | Accounting Standards Update 2015-17 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	288
Deferred Income Taxes [Member] | MidAmerican Energy Company [Member] | Accounting Standards Update 2015-17 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	1
Other Noncurrent Assets [Member] | MidAmerican Energy Company [Member] | Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	22
Long-term Debt [Member] | Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	147
Long-term Debt [Member] | MidAmerican Energy Company [Member] | Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 22