Share Repurchases (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Share Repurchases [Line Items]
Shares repurchased	757,819	4,811,346
Average price per share for repurchased shares (in dollars per share)	$ 78.09	$ 72.98
Number of treasury shares held	84,212,931	84,212,931	79,401,585
May 2012 Authorization [Member]
Share Repurchases [Line Items]
Number of shares authorized to be repurchased	10,000,000	10,000,000
Remaining number of shares authorized to be repurchased	3,908,289	3,908,289
November 2012 Authorization [Member]
Share Repurchases [Line Items]
Shares repurchased		4,805,395
Authorized dollar amount for share repurchase program	$ 1,000,000,000
Remaining dollar amount authorized to be repurchased		$ 399,000,000
Shares repurchased in open market [Member]
Share Repurchases [Line Items]
Shares repurchased	757,819	4,805,395
Shares repurchased from holders of employee stock options [Member]
Share Repurchases [Line Items]
Shares repurchased	0	5,951