Shareholders' Equity (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Shareholders' Equity
Common stock repurchased	3,900,000	48,500,000	91,800,000
Amount Shares Repurchased Under Board Authorization		1,700,000	3,000,000
Board Authorizations At An Average Price Per Share			$ 31.02
Treasury stock, shares		1,769,096	2,235,473