Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Supplemental Cash Flow Disclosures - MEC (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,016,000,000	$ 935,000,000
Restricted cash and cash equivalents	358,000,000	327,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,402,000,000	1,283,000,000	$ 1,459,000,000	$ 1,003,000,000
MidAmerican Energy Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	115,000,000	172,000,000
Restricted cash and cash equivalents	68,000,000	110,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 183,000,000	$ 282,000,000	$ 516,000,000	$ 26,000,000