Summary of Significant Accounting Policies - MEC - Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	$ 44	$ 42
MidAmerican Energy Company [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	$ 5	$ 7