Supplementary Financial Statement Information Supplementary Financial Statement Information (Interest Income and Interest Expense (Footnotes) (Details) (Variable Interest Entity, Not Primary Beneficiary [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Variable Interest Entity, Not Primary Beneficiary [Member]
Interest Income and Interest Expense [Line Items]
Interest expense and interest income excluded, amount	$ 38	$ 45	$ 49