Income Taxes - MEC - Tax Rate Change (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Rate Change [Line Items]
Deferred Tax Liabilities, Net	$ 11,775	$ 9,653
Deferred Income Tax Expense (Benefit)	1,883	296	$ 14
Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Income Tax Rate Change [Line Items]
Deferred Tax Liabilities, Net	61
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] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Income Tax Rate Change [Line Items]
Increase in Regulatory Liability	$ 59
MidAmerican Energy Company [Member]
Income Tax Rate Change [Line Items]
Deferred Tax Liabilities, Net	3,054	2,626
Deferred Income Tax Expense (Benefit)	$ 209	$ 155	$ 34