Fair Value Measurements - MEC - Level 3 (Details) - Derivative [Member] - MidAmerican Energy Company [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 3	$ (2)
Changes in fair value recognized in net regulatory assets	(2)	2
Settlements	(1)	1
Ending balance	$ 0	$ 1