Preferred Stock Preferred Stock - MEC (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
MidAmerican Energy Company [Member]
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Value	$ 28	$ 28

Equity impact of the value of stock bought back by the entity at the exercise price or redemption price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Name:	us-gaap_StockRedeemedOrCalledDuringPeriodValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration