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Income Taxes (Narrative) (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2014 | Mar. 31, 2015 | Sep. 30, 2013
Income Tax Contingency [Line Items] |  |  |  |  |
Effective tax rate | 13.00% | 59.00% | 36.00% |  |
Release of a FIN 48 reserve related to the federal research and development tax credit | $ 1,046 | $ 784 | $ 4,026 | $ 4,100 | $ 3,845
Retroactive tax benefit | 800 | 600 |  |  |
Undistributed earnings of foreign subsidiaries | 21,500 |  |  |  |
Operating loss carryforwards | $ 39,000 |  |  |  |
Operating loss carryforwards, valuation allowance |  | $ 9,300 |  |  |
Operating loss carryforwards, expiration period (in years) | 20 years |  |  |  |
Operating loss carryforwards, expiration date | 2031 |  |  |  |
Tax benefit | $ 4,100 |  |  |  |
Decrease in unrecognized tax benefits due to expiration of certain federal statutes of limitations | 32.00% |  |  |  |
Decrease in unrecognized tax benefits due to audit resolution | 33.00% |  |  |  |
R&D Tax Credit |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |
Tax credit carryforward description | On December 18, 2015, the “Protecting Americans from Tax Hikes Act of 2015” was enacted which retroactively reinstated and made permanent the R&D Tax Credit |  |  |  |

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