Stockholders' Equity (Narrative) (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended			1 Months Ended	138 Months Ended	1 Months Ended	21 Months Ended	1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2001 June 2001 Buyback Plan [Member]	Dec. 31, 2012 June 2001 Buyback Plan [Member]	Apr. 30, 2012 April 2011 Buyback Plan [Member]	Dec. 31, 2012 April 2011 Buyback Plan [Member]	Dec. 31, 2012 December 2012 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, authorized limit				$ 2,000		$ 2,000		$ 1,000
Repurchased and retired	400						284
Repurchased and retired, shares	(7,778)	(13,837)	(5,395)		(42,000)		(5,500)
Stockholders' equity tax benefit (expense)	(70)	1,365	12
Tax (expense) benefits associated with stock compensation programs	$ 51	$ 43	$ 17