Fair Value Measurements - Summary of Fair Value, Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Derivative Liability, Noncurrent	$ 245	$ 713
Interest Rate Swap [Member]
Derivative Liability, Noncurrent	(245)	(713)
Commitments [Member]
Business Combination, Contingent Consideration, Liability	(15,404)	(20,909)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Commitments [Member]
Business Combination, Contingent Consideration, Liability	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative Liability, Noncurrent	(245)	(713)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Commitments [Member]
Business Combination, Contingent Consideration, Liability	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Commitments [Member]
Business Combination, Contingent Consideration, Liability	$ (15,404)	$ (20,909)