NOTE 18. REPURCHASES OF COMMON STOCK

Our board of directors has authorized the repurchase of up to 52,000,000 shares of our common stock in the open market or in negotiated transactions. We believe that the repurchase of our common stock is a favorable means of returning value to our shareholders and we also repurchase to offset the dilutive effect of our share-based compensation programs. Repurchases of our common stock may vary depending upon the level of other investing and financing activities and the share price. As of December 31, 2013, there are 2,961,827 remaining shares available for repurchase under this authorization.

The following is a summary of our open market common stock repurchases for the years ended December 31, 2013, 2012 and 2011 (in thousands, except per share amounts):


	For the Years Ended December 31,
	2013		2012		2011

Shares repurchased		3,952		1,474		3,419
Total cost of shares repurchased	$	367,761	$	132,268	$	255,505
Average cost per share	$	93.06	$	89.72	$	74.74

We primarily acquire shares by means of repurchases in the open market. However, we also acquire shares that are surrendered by employees in payment for the minimum required withholding taxes due on the vesting of restricted stock units and the settlement of deferred stock units, otherwise referred to herein as employee surrenders. We acquired 49,475 shares at a total cost of $4.5 million in connection with employee surrenders for the year ended December 31, 2013 compared to 53,272 shares at a total cost of $4.7 million for the year ended December 31, 2012 and 55,721 shares at a total cost of $4.3 million for the year ended December 31, 2011.

In 2011, we began issuing shares of treasury stock upon the vesting of certain restricted stock units and upon the exercise of certain stock options. The number of shares of treasury stock issued during the years ended December 31, 2013, 2012 and 2011 was not material.