Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Minimum [Member] Equipment and Buildings [Member]	Dec. 31, 2013 Minimum [Member] Computer Software, Intangible Asset [Member]	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Maximum [Member] Equipment and Buildings [Member]	Dec. 31, 2013 Maximum [Member] Computer Software, Intangible Asset [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2013 Level 2 Inputs [Member]	Dec. 31, 2012 Level 2 Inputs [Member]
Summary of Significant Accounting Policies [Line Items]
Fair value of cash equivalents							$ 5,116	$ 0	$ 2,256	$ 2,026
Held-to-maturity, marketable securities, maturity timing in months	3 months			12 months
Property, Plant and Equipment, Useful Life		15 years	5 years		25 years	7 years
Definite-lived intangible assets, useful life	1 year			20 years
Asset retirement obligations, useful life	1 year			25 years