Regulatory Matters Annual Electric Distribution Filings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ (50)		$ 269		$ 353
Public Utilities, Approved Rate Increase (Decrease), Amount	67		(232)		(341)
Public Utilities, Approved Rate Increase (Decrease), Initial Revenue Requirement, Amount	85		160		160
Public Utilities, Approved Rate Increase (Decrease), Annual Reconciliation, Amount	$ (152)		$ 72		$ 181
Public Utilities, Approved Equity Capital Structure, Annual Reconciliation, Percentage	7.02%		7.04%		6.94%
Public Utilities, Approved Equity Capital Structure, Initial Revenue Requirement, Percentage	7.05%		7.06%		6.94%
Public Utilities, Approved Return on Equity, Initial Revenue Requirement, Percentage	9.14%	[1]	9.25%	[1]	8.72%
Public Utilities, Approved Return on Equity, Annual Reconciliation, Percentage	9.09%	[1]	9.20%	[1]	8.72%

[1] (a) Includes a reduction of 5 basis points for a reliability performance metric penalty.