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INCOME TAXES - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Mar. 31, 2019 | Mar. 31, 2018
Income Tax Examination [Line Items] |  |  |  |  |  |
Federal tax rate |  |  |  |  | 21.00% | 31.50%
Effective Income Tax Rate Reconciliation, Percent | (4.70%) | 10.10% | (1.40%) | 10.10% |  |
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued | $ 127.2 |  | $ 127.2 |  |  |
Unrecognized Tax Benefits that Would Impact Effective Tax Rate | 109.0 |  | 109.0 |  |  |
Income Tax Examination, Penalties and Interest Accrued | 0.9 |  | 0.9 |  |  |
Tax liability related to an settlement |  |  | 1.6 |  |  |
Deferred Tax Asset [Member] |  |  |  |  |  |
Income Tax Examination [Line Items] |  |  |  |  |  |
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued | 121.8 |  | 121.8 |  |  |
Other Noncurrent Liabilities [Member] |  |  |  |  |  |
Income Tax Examination [Line Items] |  |  |  |  |  |
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued | $ 5.4 |  | $ 5.4 |  |  |

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