BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Total Assets by Reportable Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Segment Reporting Information [Line Items]
Assets	$ 4,726,753	$ 4,829,621
Continuing Operations
Segment Reporting Information [Line Items]
Assets	4,726,753	4,829,621
Discontinued operations
Segment Reporting Information [Line Items]
Assets	0	0
Operating Segment
Segment Reporting Information [Line Items]
Assets	4,099,981	4,109,544
Investments and corporate operations
Segment Reporting Information [Line Items]
Assets	626,772	720,077
North America Solutions | Operating Segment
Segment Reporting Information [Line Items]
Assets	3,749,435	3,812,718
Offshore Gulf of Mexico | Operating Segment
Segment Reporting Information [Line Items]
Assets	98,712	93,501
International Solutions | Operating Segment
Segment Reporting Information [Line Items]
Assets	170,151	181,181
Other | Operating Segment
Segment Reporting Information [Line Items]
Assets	$ 81,683	$ 22,144