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FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENT - Assets measured at fair value and Supplemental fair value information (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Sep. 30, 2016 | Mar. 19, 2015
--- | --- | --- | ---
Liabilities: |  |  |
Contingent earnout liability | $ 14,879 |  |
Supplemental fair value information about long-term fixed-rate debt |  |  |
Carrying value of long-term fixed-rate debt | 492,902 | $ 491,847 |
Unsecured senior notes issued March 19, 2015 |  |  |
Supplemental fair value information about long-term fixed-rate debt |  |  |
Debt issued | 500,000 |  | $ 500,000
Carrying value |  |  |
Supplemental fair value information about long-term fixed-rate debt |  |  |
Carrying value of long-term fixed-rate debt | 492,900 | 491,800 |
Total Measure at Fair Value | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 44,491 |  |
Assets: |  |  |
Cash and cash equivalents | 521,375 |  |
Investments | 70,173 |  |
Other current assets | 32,439 |  |
Other assets | 6,695 |  |
Total assets measured at fair value | 675,173 |  |
Liabilities: |  |  |
Contingent earnout liability | 14,879 |  |
(Level 1) | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 24,853 |  |
Assets: |  |  |
Cash and cash equivalents | 521,375 |  |
Investments | 70,173 |  |
Other current assets | 32,189 |  |
Other assets | 6,695 |  |
Total assets measured at fair value | 655,285 |  |
(Level 2) | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 19,638 |  |
Assets: |  |  |
Other current assets | 250 |  |
Total assets measured at fair value | 19,888 |  |
(Level 2) | Total Measure at Fair Value |  |  |
Supplemental fair value information about long-term fixed-rate debt |  |  |
Fair value of long-term fixed-rate debt | 529,000 | $ 529,600 |
(Level 3) |  |  |
Liabilities: |  |  |
Contingent earnout liability | 14,879 |  |
Certificates of deposit | Total Measure at Fair Value | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 1,500 |  |
Certificates of deposit | (Level 2) | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 1,500 |  |
Corporate and municipal debt securities | Total Measure at Fair Value | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 15,818 |  |
Corporate and municipal debt securities | (Level 2) | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 15,818 |  |
U.S. government and federal agency securities | Total Measure at Fair Value | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 27,173 |  |
U.S. government and federal agency securities | (Level 1) | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | 24,853 |  |
U.S. government and federal agency securities | (Level 2) | Recurring basis |  |  |
Short-term investments: |  |  |
Short-term investments | $ 2,320 |  |

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- Definition Represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with fair value disclosures required in footnote disclosures to financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This element represents the fair value of assets categorized as other current assets which are not in and of themselves material enough to require separate disclosure. + References No definition available. + Details
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