Income Taxes Income Tax Rate Change - MEC (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Rate Change [Line Items]
Federal statutory income tax rate	21.00%	35.00%	21.00%	35.00%	35.00%
MidAmerican Energy Company [Member]
Income Tax Rate Change [Line Items]
Federal statutory income tax rate	21.00%	35.00%	21.00%	35.00%	35.00%
Tax Cuts and Jobs Act of 2017 [Member]
Income Tax Rate Change [Line Items]
Federal statutory income tax rate			21.00%
Deferred Income Tax Expense (Benefit)	$ 37
Tax Cuts and Jobs Act of 2017 [Member] | MidAmerican Energy Company [Member]
Income Tax Rate Change [Line Items]
Federal statutory income tax rate			21.00%
Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Income Tax Rate Change [Line Items]
Deferred Tax Liabilities, Net	61		$ 61
Deferred Income Tax Expense (Benefit)			2
Iowa Senate File 2417, Rate Effective Starting 2021 [Member] | MidAmerican Energy Company [Member]
Income Tax Rate Change [Line Items]
Deferred Tax Liabilities, Net	54		54
Deferred Income Tax Expense (Benefit)			$ 2
Maximum [Member] | IOWA | Tax Year, Current [Member]
Income Tax Rate Change [Line Items]
Statutory Income Tax Rate, State and Local, Percent			12.00%
Maximum [Member] | IOWA | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Income Tax Rate Change [Line Items]
Statutory Income Tax Rate, State and Local, Percent			9.80%
Deferred Income Tax Charge [Member] | Tax Cuts and Jobs Act of 2017 [Member]
Income Tax Rate Change [Line Items]
Increase in Regulatory Liability	$ 14
Deferred Income Tax Charge [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Income Tax Rate Change [Line Items]
Increase in Regulatory Liability			$ 59
Deferred Income Tax Charge [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member] | MidAmerican Energy Company [Member]
Income Tax Rate Change [Line Items]
Increase in Regulatory Liability			$ 56