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FAIR VALUE MEASUREMENT OF FINANCIAL INSTRUMENTS - Narrative (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fixed-rate debt | $ 487,148,000 | $ 487,148,000
Gain resulting from increases in the fair value of investments | 2,800,000 |
Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets held in a non-qualified supplemental savings plan | 16,100,000 | $ 15,700,000
Level 2 | Carrying Value |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fixed-rate debt | 487,100,000 |
MOTIVE Drilling Technologies, Inc. | Level 3 | Recurring Fair Value Measurements |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Contingent consideration | $ 0 |

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