Stockholders' Equity (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended		126 Months Ended	1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2001 June 2001 Buyback Plan [Member]	Dec. 31, 2011 June 2001 Buyback Plan [Member]	Dec. 31, 2010 June 2001 Buyback Plan [Member]	Dec. 31, 2011 June 2001 Buyback Plan [Member]	Apr. 30, 2011 April 2011 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, authorized limit				$ 2,000				$ 2,000
Repurchased and retired					672	250	1,884
Repurchased and retired, shares	13,837,000	5,395,000			13,800,000	5,400,000	39,700,000
Stockholders' equity tax benefit (expense)	1,365	12	144
Tax (expense) benefits associated with stock compensation programs	$ 43	$ 17	$ (10)