Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Assets:
Available-for-sale securities	$ 6,125	$ 133,308
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	59	11,628
Available-for-sale securities	6,125	133,308
Foreign exchange contracts	116	89
Stock warrant	49	59
Total Assets	12,045	150,421
Liabilities
Contingent consideration	500	811
Foreign exchange contracts	116	36
Total Liabilities	616	847
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	59	10,133
Available-for-sale securities	0	0
Foreign exchange contracts	0	0
Stock warrant	0	0
Total Assets	59	10,133
Liabilities
Contingent consideration	0	0
Foreign exchange contracts	0	0
Total Liabilities	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0	1,495
Available-for-sale securities	6,125	133,308
Foreign exchange contracts	116	89
Stock warrant	0	0
Total Assets	6,241	134,892
Liabilities
Contingent consideration	0	0
Foreign exchange contracts	116	36
Total Liabilities	116	36
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0	0
Available-for-sale securities	0	0
Foreign exchange contracts	0	0
Stock warrant	49	59
Total Assets	5,745	5,396
Liabilities
Contingent consideration	500	811
Foreign exchange contracts	0	0
Total Liabilities	500	811
Convertible Debt Securities | Fair Value, Measurements, Recurring
Assets:
Convertible debt securities	5,696	5,337
Convertible Debt Securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets:
Convertible debt securities	0	0
Convertible Debt Securities | Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets:
Convertible debt securities	0	0
Convertible Debt Securities | Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets:
Convertible debt securities	$ 5,696	$ 5,337