Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Share Repurchases [Line Items]
Shares repurchased		289,930		3,886,910
Average price per share for repurchased shares (in dollars per share)	$ 75.68	$ 86.25	$ 74.44	$ 81.70
Number of treasury shares held	99,599,062		99,599,062		92,880,644
Purchase of common stock	$ 300,079	$ 25,006	$ 500,134	$ 317,571
January 2015 Authorization [Member]
Share Repurchases [Line Items]
Number of shares authorized to be repurchased	15,000,000		15,000,000
Shares repurchased	3,965,253		6,718,418
Remaining number of shares authorized to be repurchased	8,281,582		8,281,582
November 2012 Authorization [Member]
Share Repurchases [Line Items]
Authorized dollar amount for share repurchase program		$ 1,000,000		$ 1,000,000