Litigation, Claims and Contingencies - Summary of Asbestos Claims Activity (Details) - Claim Claim in Thousands	9 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Ashland [Member]
Asbestos claims [Roll Forward]
Open claims - beginning of year	53	54	54	57	60
New claims filed	2	2	2	2	2
Claims settled	(1)	(1)	(1)	(1)	0
Claims dismissed	(1)	(2)	(2)	(4)	(5)
Open claims - end of period	53	53	53	54	57
Hercules [Member]
Asbestos claims [Roll Forward]
Open claims - beginning of year	13	12	12	15	20
New claims filed		1	2	1	1
Claims dismissed	(1)	(1)	(1)	(4)	(6)
Open claims - end of period	12	12	13	12	15