Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Assets:
Available-for-sale securities	$ 9,655	$ 133,308
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	2,702	11,628
Available-for-sale securities	9,655	133,308
Foreign exchange contracts	87	89
Stock warrants	51	59
Total Assets	18,091	150,421
Liabilities
Contingent consideration	733	811
Foreign exchange contracts	100	36
Total Liabilities	833	847
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	2,702	10,133
Available-for-sale securities	0	0
Foreign exchange contracts	0
Stock warrants	0	0
Total Assets	2,702	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	9,655	133,308
Foreign exchange contracts	87	89
Stock warrants	0	0
Total Assets	9,742	134,892
Liabilities
Contingent consideration	0	0
Foreign exchange contracts	100	36
Total Liabilities	100	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 warrants	51	59
Total Assets	5,647	5,396
Liabilities
Contingent consideration	733	811
Foreign exchange contracts	0	0
Total Liabilities	733	811
Convertible Debt Securities | Fair Value, Measurements, Recurring
Assets:
Convertible debt securities	5,596	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	$ 5,596	$ 5,337