Stock Repurchase Program	12 Months Ended
Dec. 31, 2017
Stock Repurchase Program	S. STOCK REPURCHASE PROGRAM In January 2015, Teradyne’s Board of Directors cancelled the November 2010 stock repurchase program and authorized a new stock repurchase program for up to $500 million of common stock. In 2015, Teradyne repurchased 15.6 million shares of common stock at an average price of $19.20, for a total cost of $300 million. In 2016, Teradyne repurchased 6.8 million shares of common stock at an average price of $21.39, for a total cost of $146 million. The cumulative repurchases as of December 31, 2016 totaled 22.5 million shares of common stock for $446 million at an average price per share of $19.87. In December 2016, Teradyne’s Board of Directors cancelled the January 2015 stock repurchase program and approved a new $500 million share repurchase authorization which commenced on January 1, 2017. The cumulative repurchases as of December 31, 2017 totaled 5.8 million shares of common stock for $200 million at an average price per share of $34.30.

S. STOCK REPURCHASE PROGRAM

In January 2015, Teradyne’s Board of Directors cancelled the November 2010 stock repurchase program and authorized a new stock repurchase program for up to $500 million of common stock. In 2015, Teradyne repurchased 15.6 million shares of common stock at an average price of $19.20, for a total cost of $300 million. In 2016, Teradyne repurchased 6.8 million shares of common stock at an average price of $21.39, for a total cost of $146 million. The cumulative repurchases as of December 31, 2016 totaled 22.5 million shares of common stock for $446 million at an average price per share of $19.87.

In December 2016, Teradyne’s Board of Directors cancelled the January 2015 stock repurchase program and approved a new $500 million share repurchase authorization which commenced on January 1, 2017. The cumulative repurchases as of December 31, 2017 totaled 5.8 million shares of common stock for $200 million at an average price per share of $34.30.