Stockholders' equity	12 Months Ended
Stockholders' equity	Dec. 31, 2012
Equity [Abstract]
Stockholders' equity	Stockholders’ equity We are authorized to issue 10,000,000 shares of preferred stock. No preferred stock is currently outstanding. Treasury shares acquired in connection with the board-authorized stock repurchase program in 2012, 2011 and 2010 were 59,757,780 shares, 59,466,168 shares and 93,522,896 shares, respectively. As of December 31, 2012, $3.9 billion of stock repurchase authorizations remain, and no expiration date has been specified.

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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