Share Repurchases (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Share Repurchases [Line Items]
Shares repurchased	649,840	5,461,186
Average price per share for repurchased shares (in dollars per share)	$ 87.33	$ 74.68
Number of treasury shares held	84,862,771	84,862,771	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		5,455,235
Authorized dollar amount for share repurchase program	$ 1,000,000,000
Remaining dollar amount authorized to be repurchased		$ 342,565,000
Shares repurchased in open market [Member]
Share Repurchases [Line Items]
Shares repurchased	649,840	5,455,235
Shares repurchased from holders of employee stock options [Member]
Share Repurchases [Line Items]
Shares repurchased	0	5,951