Share Repurchases	3 Months Ended
Share Repurchases	Mar. 31, 2012
Share Repurchases [Abstract]
Share Repurchases	17. Share Repurchases In May 2007, the Board of Directors authorized the repurchase of up to 10,000,000 shares through May 2012. During the three months ended March 31, 2012, the Company repurchased 660,000 shares of its common stock in the open market. During the three months ended March 31, 2012, the Company also repurchased 43,931 shares from the holders of its employee stock options when they tendered these shares as full or partial payment of the exercise price of such options. Therefore, during the three months ended March 31, 2012, a total of 703,931 shares were repurchased at a cumulative average price of $64.15 per share. Treasury shares increased to 67,704,418 at March 31, 2012 from a balance of 67,000,487 at December 31, 2011.

Tabular disclosure of an entity's treasury stock, including the average cost per share, carrying basis for each class of treasury stock, description of share repurchase program authorized by an entity's board of directors, the number of shares repurchased, the cost of the shares repurchased, the remaining maximum dollar value of shares available for repurchase under the program, the treatment of the purchase price in excess of the current market value, number of shares held for each class of treasury stock, and other information necessary to a fair presentation.

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