v3.26.1
Earnings Per Share - Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS) (Detail) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Basic EPS:        
Net income (loss) attributable to Cabot Corporation $ 6 $ 101 $ 147 $ 288
Less: Dividends and dividend equivalents to participating securities       1
Less: Undistributed earnings allocated to participating securities   1 2 3
Earnings (loss) allocated to common stockholders (numerator) $ 6 $ 100 $ 145 $ 284
Weighted average common shares and participating securities outstanding 52.3 54.2 52.9 54.7
Less: Participating securities 0.7 0.7 0.8 0.8
Adjusted weighted average common shares (denominator) 51.6 53.5 52.1 53.9
Earnings (loss) per common share - basic: $ 0.12 $ 1.87 $ 2.79 $ 5.27
Diluted EPS:        
Earnings (loss) allocated to common stockholders $ 6 $ 100 $ 145 $ 284
Plus: Earnings allocated to participating securities   1 2 4
Less: Adjusted earnings allocated to participating securities   1 2 4
Earnings (loss) allocated to common stockholders (numerator) $ 6 $ 100 $ 145 $ 284
Adjusted weighted average common shares outstanding 51.6 53.5 52.1 53.9
Common shares issuable 0.4 0.3 0.3 0.5
Adjusted weighted average common shares (denominator) 52.0 53.8 52.4 54.4
Earnings (loss) per common share - diluted: $ 0.12 $ 1.86 $ 2.77 $ 5.22