BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Total Assets by Reportable Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Assets	$ 4,962,326	$ 5,839,515
Continuing Operations
Segment Reporting Information [Line Items]
Assets	4,962,326	5,839,515
Discontinued Operations
Segment Reporting Information [Line Items]
Assets	0	0
Operating Segment
Segment Reporting Information [Line Items]
Assets	4,316,779	5,636,209
Investments and Corporate Operations
Segment Reporting Information [Line Items]
Assets	645,547	203,306
North America Solutions | Operating Segment
Segment Reporting Information [Line Items]
Assets	3,990,736	5,284,141
Offshore Gulf of Mexico | Operating Segment
Segment Reporting Information [Line Items]
Assets	104,262	102,442
International Solutions | Operating Segment
Segment Reporting Information [Line Items]
Assets	188,126	217,094
Other | Operating Segment
Segment Reporting Information [Line Items]
Assets	$ 33,655	$ 32,532