Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Supplemental Cash Flow Disclosures - MEC (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,644,000,000	$ 935,000,000
Restricted cash and cash equivalents	212,000,000	327,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,876,000,000	1,283,000,000	$ 1,232,000,000	$ 1,003,000,000
MidAmerican Energy Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	380,000,000	172,000,000
Restricted cash and cash equivalents	98,000,000	110,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 478,000,000	$ 282,000,000	$ 491,000,000	$ 26,000,000