Risk Management and Hedging Activities - MEC - Designated as Hedging Activities (Details) - Commodity Contract [Member] - Designated as Hedging Instrument [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive (Income) Loss, Net, Derivatives [Roll Forward]
Beginning balance	$ 16	$ 46	$ 32
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(15)	(26)	(52)
Ending balance	0	16	46
MidAmerican Energy Company [Member]
Accumulated Other Comprehensive (Income) Loss, Net, Derivatives [Roll Forward]
Beginning balance	0	45	34
Cumulative Net Gain (Loss) From Cash Flow Hedges, Before Taxes Transferred to Affiliate	0	(45)	0
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	0	0	58
Cash Flow Hedge Gain (Loss) Reclassified To Cost Of Sales Nonregulated	0	0	(47)
Ending balance	$ 0	$ 0	$ 45