Regulatory Matters - MEC - Regulatory Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory liabilities		$ 7,309	$ 2,933
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[1]	26.845466155811
Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[2]	Various
Asset Retirement Obligation Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		34.638418079096
Pension and other postretirement costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[3]	10.6086956521739
Unrealized gain on regulated derivative contracts [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		1
MidAmerican Energy Company [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities		$ 1,661	883
MidAmerican Energy Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[4]	28 years
Regulatory liabilities	[4]	$ 688	665
MidAmerican Energy Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[5]	28 years
Regulatory liabilities	[5]	$ 681	0
MidAmerican Energy Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[5]	35 years
Regulatory liabilities	[5]	$ 173	117
MidAmerican Energy Company [Member] | Transmission MVP CWIP Return [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[6]	55 years
Regulatory liabilities	[6]	$ 35	35
MidAmerican Energy Company [Member] | Regulatory revenue sharing arrangement [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[7]	1 year
Regulatory liabilities	[7]	$ 26	30
MidAmerican Energy Company [Member] | Pension and other postretirement costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[8]	11 years
Regulatory liabilities	[8]	$ 41	12
MidAmerican Energy Company [Member] | Unrealized gain on regulated derivative contracts [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		1 year
Regulatory liabilities		$ 3	6
MidAmerican Energy Company [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		Various
Regulatory liabilities		$ 14	$ 18

[1] Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.

[2] (1)Amounts primarily represent income tax liabilities related to the federal tax rate change from 35% to 21% that are probable to be passed on to customers, offset by income tax benefits related to certain property-related basis differences and other various differences that were previously passed on to customers and will be included in regulated rates when the temporary differences reverse. See Note 11 for further discussion of 2017 Tax Reform impacts.

[3] (3)Represents amounts not yet recognized as a component of net periodic benefit cost that are to be returned to customers in future periods when recognized.

[4] (1)Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing utility plant in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.

[5] (3)Amount predominantly represents the excess of nuclear decommission trust assets over the related asset retirement obligation. Refer to Note 12 for a discussion of asset retirement obligations.

[6] (4)Represents amounts not yet recognized as a component of net periodic benefit cost that are to be returned to customers in future periods when recognized.

[7] (5)Represents AFUDC accrued on transmission MVPs that is deducted from rate base as a result of the inclusion of related construction work-in-progress in rate base.

[8] (6)Represents current-year accruals under a regulatory arrangement in Iowa in which equity returns exceeding specified thresholds reduce utility plant upon final determination.