v3.26.1
Financial Information by Segment - Revenue from External Customers by Geographic Region (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting Information [Line Items]        
Net sales and other operating revenues $ 982 $ 923 $ 2,735 $ 2,814
Operating Segments [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 950 893 2,642 2,720
Unallocated and Other [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 32 30 93 94
Americas [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 351 328 943 997
Asia Pacific [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 372 331 1,062 1,059
Europe, Middle East and Africa [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 227 234 637 664
Reinforcement Materials [Member] | Operating Segments [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 599 573 1,663 1,778
Reinforcement Materials [Member] | Americas [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 245 230 661 714
Reinforcement Materials [Member] | Asia Pacific [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 219 199 617 659
Reinforcement Materials [Member] | Europe, Middle East and Africa [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 135 144 385 405
Performance Chemicals [Member] | Operating Segments [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 351 320 979 942
Performance Chemicals [Member] | Americas [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 106 98 282 283
Performance Chemicals [Member] | Asia Pacific [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues 153 132 445 400
Performance Chemicals [Member] | Europe, Middle East and Africa [Member]        
Segment Reporting Information [Line Items]        
Net sales and other operating revenues $ 92 $ 90 $ 252 $ 259