Fair Value Measurements (Assets Measured at Fair Value on a Recurring Basis) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Mar. 31, 2016 | Sep. 30, 2015 |
Estimate of Fair Value Measurement [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | $ 45,451 | $ 54,180 |
Estimate of Fair Value Measurement [Member] | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 32,799 | 24,369 |
Estimate of Fair Value Measurement [Member] | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 3,960 | 11,594 |
Estimate of Fair Value Measurement [Member] | Municipal bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 4,900 | 13,903 |
Estimate of Fair Value Measurement [Member] | Commercial Paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 2,501 | |
Estimate of Fair Value Measurement [Member] | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 1,291 | 4,314 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 36,759 | 35,963 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 32,799 | 24,369 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 3,960 | 11,594 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial Paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 8,692 | 18,217 |
Significant Other Observable Inputs (Level 2) | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Municipal bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 4,900 | 13,903 |
Significant Other Observable Inputs (Level 2) | Commercial Paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 2,501 | |
Significant Other Observable Inputs (Level 2) | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 1,291 | 4,314 |
Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Municipal bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Commercial Paper [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | 0 | |
Significant Unobservable Inputs (Level 3) | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Total assets at fair value on a recurring basis | $ 0 | $ 0 |