Shareholders Equity (Details 2) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Treasury Stock [Roll Forward]
Treasury Stock, Shares, Beginning (in shares)	15,508
Treasury Stock, Value, Beginning	$ 124
Treasury Stock, Shares, Acquired	47,429	[1]
Treasury Stock, Value, Acquired, Cost Method	357	[1]
Treasury Stock, Shares, Retired	(22,098)
Treasury Stock, Retired, Cost Method, Amount	0
Treasury Stock, Shares, Ending (in shares)	40,839
Treasury Stock, Value, Ending	303
Treasury Stock [Member]
Treasury Stock [Roll Forward]
Treasury Stock, Value, Acquired, Cost Method	357
Treasury Stock, Retired, Cost Method, Amount	$ (178)

[1] (1)Includes associated fees.