Reportable Segment Information - Geographic Revenue and Long-lived Assets (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| U.S. [Member] | |||
| Revenues from External Customers and Long-Lived Assets [Line Items] | |||
| Long-lived assets, including property and equipment and intangible assets net of accumulated depreciation and amortization | $ 20,949 | $ 21,543 | |
| Ireland [Member] | |||
| Revenues from External Customers and Long-Lived Assets [Line Items] | |||
| Long-lived assets, including property and equipment and intangible assets net of accumulated depreciation and amortization | $ 22,555 | $ 20,583 | |
| Revenue [Member] | Geographic Concentration Risk [Member] | Domestic [Member] | |||
| Revenues from External Customers and Long-Lived Assets [Line Items] | |||
| Percentage of revenue | 77.00% | 79.00% | 77.00% |
| Revenue [Member] | Geographic Concentration Risk [Member] | Foreign [Member] | |||
| Revenues from External Customers and Long-Lived Assets [Line Items] | |||
| Percentage of revenue | 23.00% | 21.00% | 23.00% |