STOCK-BASED COMPENSATION - Narrative (Details) $ in Thousands	3 Months Ended
Dec. 31, 2019 USD ($) component tranche shares	Dec. 31, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 10,201	$ 7,158
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of units vested	0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of units vested	200.00%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period over which awards expire	10 years
Stock-based compensation expense	$ 571	1,416
Total intrinsic value of options exercised	300	7,600
Unrecognized compensation cost related to stock options	$ 2,700
Weighted average period over which unrecognized compensation cost is expected to be recognized	1 year 9 months 18 days
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7,370	5,742
Unrecognized compensation cost related to non-option awards	$ 57,800
Weighted average period over which unrecognized compensation cost is expected to be recognized	3 years 1 month 6 days
Vesting period	4 years
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,260	0
Unrecognized compensation cost related to non-option awards	$ 13,600
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years 2 months 12 days
Vesting period	3 years
Performance components \| component	2
Performance Share Units - First Component
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period over which awards expire	3 years
Performance Share Units - Second Component
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period over which awards expire	3 years
Number of tranches \| tranche	3
Performance cycle period of each tranche	1 year
Contract Drilling Services Operating Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,400	1,600
Selling, General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7,800	$ 5,600
2016 Plan \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) \| shares	0
2016 Plan \| Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) \| shares	727,009
2016 Plan \| Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) \| shares	258,857

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Gross number of share options (or share units) granted during the period.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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