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		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 14,291	$ 9,308	$ 14,517
Additions		3,517		$ 12,581
Fair value adjustments	(1,159)		(1,159)
Interest accretion	548	392	985	501
Foreign currency translation loss (gain)	190	429	(473)	564
Ending balance	$ 13,870	$ 13,646	$ 13,870	$ 13,646