v3.25.2
Revenue - Summary of Percentage of Ashland's Total Consolidated Sales by Product (Details) - Sales Revenue [Member] - Product Concentration Risk [Member]
3 Months Ended 9 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Cellulosics and PVP [Member]        
Revenue From Contracts With Customers [Line Items]        
Concentration risk percentage 65.00% 57.00% 64.00% 59.00%
Cellulosics [Member]        
Revenue From Contracts With Customers [Line Items]        
Concentration risk percentage 40.00% 36.00% 39.00% 37.00%
PVP [Member]        
Revenue From Contracts With Customers [Line Items]        
Concentration risk percentage 25.00% 21.00% 25.00% 22.00%