Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation Of Revenue [Line Items]
Sales	$ 497	$ 463	$ 1,365	$ 1,347
Life Sciences [Member]
Disaggregation Of Revenue [Line Items]
Sales	180	162	491	468
Life Sciences [Member] \| North America [Member]
Disaggregation Of Revenue [Line Items]
Sales	33	31	92	84
Life Sciences [Member] \| Europe [Member]
Disaggregation Of Revenue [Line Items]
Sales	71	60	188	179
Life Sciences [Member] \| Asia Pacific [Member]
Disaggregation Of Revenue [Line Items]
Sales	56	52	155	151
Life Sciences [Member] \| Latin America & Other [Member]
Disaggregation Of Revenue [Line Items]
Sales	20	19	56	54
Personal Care [Member]
Disaggregation Of Revenue [Line Items]
Sales	155	147	428	426
Personal Care [Member] \| North America [Member]
Disaggregation Of Revenue [Line Items]
Sales	39	35	107	116
Personal Care [Member] \| Europe [Member]
Disaggregation Of Revenue [Line Items]
Sales	59	59	165	163
Personal Care [Member] \| Asia Pacific [Member]
Disaggregation Of Revenue [Line Items]
Sales	38	34	102	94
Personal Care [Member] \| Latin America & Other [Member]
Disaggregation Of Revenue [Line Items]
Sales	19	19	54	53
Specialty Additives [Member]
Disaggregation Of Revenue [Line Items]
Sales	136	131	372	380
Specialty Additives [Member] \| North America [Member]
Disaggregation Of Revenue [Line Items]
Sales	48	47	127	133
Specialty Additives [Member] \| Europe [Member]
Disaggregation Of Revenue [Line Items]
Sales	48	48	127	130
Specialty Additives [Member] \| Asia Pacific [Member]
Disaggregation Of Revenue [Line Items]
Sales	34	30	98	97
Specialty Additives [Member] \| Latin America & Other [Member]
Disaggregation Of Revenue [Line Items]
Sales	6	6	20	20
Intermediates [Member]
Disaggregation Of Revenue [Line Items]
Sales	37	33	103	104
Intermediates [Member] \| North America [Member]
Disaggregation Of Revenue [Line Items]
Sales	24	21	68	69
Intermediates [Member] \| Europe [Member]
Disaggregation Of Revenue [Line Items]
Sales	7	9	17	20
Intermediates [Member] \| Asia Pacific [Member]
Disaggregation Of Revenue [Line Items]
Sales	4	2	12	10
Intermediates [Member] \| Latin America & Other [Member]
Disaggregation Of Revenue [Line Items]
Sales	$ 2	$ 1	$ 6	$ 5