Income Taxes Income Taxes - MEC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of Income Tax Expense (Benefit) [Line Items]
Current Federal Tax Expense (Benefit)	$ (653)	$ (743)	$ (929)
Current State and Local Tax Expense (Benefit)	(3)	1	29
Current Income Tax Expense (Benefit)	(573)	(687)	(816)
Deferred Federal Income Tax Expense (Benefit)	(76)	1,164	1,310
Deferred State and Local Income Tax Expense (Benefit)	100	(59)	(53)
Deferred Income Tax Expense (Benefit)	26	1,098	1,274
Other Tax Expense (Benefit)	(7)	(8)	(8)
Income tax (benefit) expense	(554)	403	450
MidAmerican Energy Company [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Current Federal Tax Expense (Benefit)	(490)	(479)	(415)
Current State and Local Tax Expense (Benefit)	(25)	(14)	(6)
Current Income Tax Expense (Benefit)	(515)	(493)	(421)
Deferred Federal Income Tax Expense (Benefit)	335	366	281
Deferred State and Local Income Tax Expense (Benefit)	(2)	(4)	(6)
Deferred Income Tax Expense (Benefit)	333	362	275
Other Tax Expense (Benefit)	(1)	(1)	(1)
Income tax (benefit) expense	$ (183)	$ (132)	$ (147)