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Property and Equipment (Narratives) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			4 Months Ended	5 Months Ended	6 Months Ended	9 Months Ended
	Apr. 30, 2021	Jun. 30, 2022	Mar. 31, 2022	Mar. 31, 2021	Apr. 30, 2021	Sep. 30, 2021	Jun. 30, 2023	Sep. 30, 2022
Property, Plant and Equipment [Line Items]
Loss on impairment		$ 34.5			$ 756.5	$ 0.0		$ 34.5
Gain (Loss) on Disposition of Other Assets	$ 5.3		$ 2.0
Net proceeds from disposition of assets		7.0			30.1	$ 1.5		146.8
Operating Segments [Member] \| Jackups
Property, Plant and Equipment [Line Items]
Loss on impairment					$ 0.0			$ 0.0
Operating Segments [Member] \| Jackups \| V54 \| Forecast
Property, Plant and Equipment [Line Items]
Gain (Loss) on Disposition of Other Assets							$ 28.0
Operating Segments [Member] \| Jackups \| V113 & V114
Property, Plant and Equipment [Line Items]
Gain (Loss) on Disposition of Other Assets		120.0
Operating Segments [Member] \| Jackups \| V36
Property, Plant and Equipment [Line Items]
Gain (Loss) on Disposition of Other Assets		$ 8.5
Foreign Exchange Forward
Property, Plant and Equipment [Line Items]
Gain (Loss) Reclassified from Accumulated Other Comprehensive Income ("AOCI") into Income (Effective Portion)				$ 5.6
Floaters
Property, Plant and Equipment [Line Items]
Loss on impairment				756.5
Property, Plant, and Equipment, Fair Value Disclosure				$ 26.0