Summary Of Significant Accounting Policies (Schedule Of Goodwill By Reporting Segment) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Goodwill	$ 5,858	$ 6,079
United States [Member]
Summary Of Significant Accounting Policies [Line Items]
Goodwill	3,020	3,046
Canada [Member]
Summary Of Significant Accounting Policies [Line Items]
Goodwill	$ 2,838	$ 3,033