PROPERTY, PLANT AND EQUIPMENT - Depreciation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Property, Plant and Equipment
Depreciation	$ 141.9	$ 143.1	$ 423.6	$ 430.0
Abandonments	$ 1.4	$ 7.0	6.8	$ 22.5
Increase in depreciation expense in next three months			0.7
Decrease in depreciation expense in year 2020			0.8
Decrease in depreciation expense in year 2021			0.8
Decrease in depreciation expense in year 2022			0.6
Decrease in depreciation expense in year 2023			0.3
Decrease in depreciation expense in year 2024			0.3
Decrease in depreciation expense thereafter			0.5
Rigs components depreciation
Property, Plant and Equipment
Increase in depreciation			$ 4.5