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	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 13,345	$ 13,870	$ 14,864	$ 14,517
Fair value adjustments	21	(1,192)	(1,278)	(2,350)
Settlements			(925)
Interest accretion	85	563	272	1,547
Foreign currency translation loss (gain)	(592)	600	(74)	127
Ending balance	$ 12,859	$ 13,841	$ 12,859	$ 13,841