Restructuring - Summary of Restructuring Expense and Gains (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost And Reserve [Line Items]
Restructuring expense and gain	$ (682)	$ 33,615	$ 22,679
Restructuring charges	(682)	33,615	22,679
Supply Chain Modernization
Restructuring Cost And Reserve [Line Items]
Restructuring expense and gain	(4,662)
Restructuring charges	3,747
2018 Restructuring Plan
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 3,980	$ 33,615
2017 Restructuring Plan
Restructuring Cost And Reserve [Line Items]
Restructuring charges			$ 22,679