Merger-Related Activities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Merger-related expenses	$ 0	$ 20	$ 0
BHE Merger
Business Acquisition [Line Items]
One-time bill credit		5
Merger-related expenses		20
Change in Control Costs [Member] | BHE Merger
Business Acquisition [Line Items]
Merger-related expenses		6
Stock Compensation Plan [Member] | BHE Merger
Business Acquisition [Line Items]
Merger-related expenses		7
Investment Banker Fees [Member] | BHE Merger
Business Acquisition [Line Items]
Merger-related expenses		6
Legal Fees and Other Expenses [Member] | BHE Merger
Business Acquisition [Line Items]
Merger-related expenses		$ 1