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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - SALES TAX ACCOUNTING (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Mar. 31, 2018 | Mar. 31, 2017 | Jan. 01, 2018 | Jan. 01, 2017
Principal Transaction Revenue [Line Items] |  |  |  |  |  |
Sales tax | $ 18.7 | $ 16.9 | $ 31.9 | $ 28.1 |  |
NEW JERSEY |  |  |  |  |  |
Principal Transaction Revenue [Line Items] |  |  |  |  |  |
State sales tax, percent |  | 7.00% |  | 7.00% | 6.625% | 6.875%

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- Definition State Sales Tax, Percent + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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