Summary of Significant Accounting Policies Summary of Significant Accounting Policies - MEC - New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	$ 44	$ 42
MidAmerican Energy Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	5	7
Energy Related Inventory, Gas Stored Underground	28	24
Adjustment clause accounts receivable (payable)	$ 56	$ 56