Restructuring - Summary of Restructuring Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 687	$ 2,839	$ 8,706
Restructuring Charges Excluding CEO Transition Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	687	2,839	6,332
Restructuring Charges Excluding CEO Transition Costs [Member] | Severance, Other Termination Benefits and Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	601	2,046	5,012
Restructuring Charges Excluding CEO Transition Costs [Member] | Lease and Other Contract Termination Fees [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	86	54	353
Restructuring Charges Excluding CEO Transition Costs [Member] | Loss on Fixed Asset Disposals and Inventory Scrap [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		528	225
Restructuring Charges Excluding CEO Transition Costs [Member] | Other [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 0	$ 211	$ 742