Fair Value Measurements - Schedule of Contingent Consideration Liabilities Measured at Fair Value (Detail) - Contingent Consideration [Member] - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Contingent consideration liability, beginning balance	$ 3,200	$ 14,466
Fair value adjustments		(415)
Settlements	$ (3,200)	(10,979)
Interest accretion		254
Foreign currency translation		(126)
Contingent consideration liability, ending balance		$ 3,200