v3.26.3
Computation of Basic and Diluted Earnings Per Common Share Attributable to Teradyne (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 27, 2026
Sep. 28, 2025
Sep. 27, 2026
Sep. 28, 2025
Net Income Loss Per Common Share        
Net Income (Loss) $ 342,407 $ 119,558 $ 1,115,849 $ 296,827
Weighted average common shares-basic 156,262 158,595 156,381 160,021
Employee stock purchase plan 2 3 2 19
Dilutive potential common shares 1,240 502 1,229 388
Weighted average common shares-diluted 157,502 159,097 157,610 160,409
Earnings per common share attributable to Teradyne - basic $ 2.19 $ 0.75 $ 7.14 $ 1.85
Earnings per common share attributable to Teradyne - diluted $ 2.17 $ 0.75 $ 7.08 $ 1.85
Restricted Stock Units        
Net Income Loss Per Common Share        
Incremental shares attributable to share based payment arrangements 1,159 495 1,149 366
Employee Stock Option [Member]        
Net Income Loss Per Common Share        
Incremental shares attributable to share based payment arrangements 79 4 78 3