Debt (Narrative) (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	May 03, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	May 03, 2013
Proceeds from Debt, Net of Issuance Costs	$ 494
Interest Costs Incurred		548	625	683
Interest Paid		551	614	626
Total debt		9,635	10,409
Customer Financing [Member]
Debt Instrument [Line Items]
Customer Financing Asset Used For Collateralizing Debt		404
Secured Debt [Member]
Debt Instrument [Line Items]
Total debt		256
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Available amount under credit facility		4,845
Revolving Credit Facility [Member] | 364-day Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Available amount under credit facility		2,392
Maturity date of credit line agreements		Nov. 06, 2014
Revolving Credit Facility [Member] | Five Year Credit Facility [Member]
Debt Instrument [Line Items]
Available amount under credit facility		2,453
Revolving Credit Facility [Member] | Five Year Credit Facility [Member] | Five Year Expiration [Member]
Debt Instrument [Line Items]
Available amount under credit facility		2,393
Maturity date of credit line agreements		Nov. 10, 2018
Revolving Credit Facility [Member] | Five Year Credit Facility [Member] | Four Year Expiration [Member]
Debt Instrument [Line Items]
Available amount under credit facility		60
Maturity date of credit line agreements		Nov. 10, 2017
Zero Point Nine Five Percent Due May 15, 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	350
Debt maturity date	May 15, 2018
Debt Instrument, Interest Rate, Stated Percentage	0.95%
Floating Rate Due November 3, 2014 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 150
Debt maturity date	Nov. 03, 2014
Debt Instrument, Description of Variable Rate Basis	three-month LIBOR