Stockholders' Equity (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		1 Months Ended		6 Months Ended	1 Months Ended	132 Months Ended	1 Months Ended	26 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Feb. 28, 2013 December 2012 Buyback Plan [Member]	Dec. 31, 2012 December 2012 Buyback Plan [Member]	Jun. 30, 2013 December 2012 Buyback Plan [Member]	Jun. 30, 2001 June 2001 Buyback Plan [Member]	Jun. 30, 2012 June 2001 Buyback Plan [Member]	Apr. 30, 2011 April 2011 Buyback Plan [Member]	Jun. 30, 2013 April 2011 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Payment for the repurchase of common stock	$ 1,000	$ 400	$ 1,000
Stock Repurchase Program, Authorized Amount				1,000		2,000		2,000
Stock Repurchased and Retired During Period, Shares		7.8			20.4		42.0		5.5
Stock Repurchased and Retired During Period, Value									$ 284