Shareholders' Equity

12 Months Ended

Dec. 31, 2017

5. Shareholders’ Equity

Through December 31, 2017, we had announced authorizations by our Board of Directors of repurchases of shares of common stock, which in the aggregate, authorized expenditures of up to $2,400,000. Under the remaining repurchase authorizations, shares may be purchased from time to time in open market transactions, subject to market conditions.

The following table summarizes common stock repurchases under authorized programs:



	Year ended December 31,
	2017		2016		2015
Shares of common stock repurchased		805		1,811		839
Total cost of common stock repurchased	$	284,318	$	813,881	$	485,841

As of December 31, 2017, $118,274 was available to be repurchased under the authorized programs. The shares repurchased are being held in treasury until such time as they are reissued or retired, at the discretion of the Board of Directors.

During 2017, 2016, and 2015, shares of common stock were netted and surrendered as payment for minimum statutory tax withholding obligations in connection with the exercise and vesting of outstanding stock awards. We deem shares surrendered by the participants in accordance with the applicable award agreements and plan as repurchased, but do not deem such shares to be part of publicly announced share repurchase programs.