Discontinued Operations - Interest and Amortization (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense	$ 12.4	$ 19.1	$ 33.8	$ 38.3
Revolving Credit Agreement | Marine Services | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense	0.0	0.0	0.0	0.2
Amortization of deferred financing costs and original issuance discount	0.0	0.0	0.0	0.1
Secured Indenture | Marine Services | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense	0.0	0.0	0.0	2.2
Amortization of deferred financing costs and original issuance discount	0.0	0.0	0.0	0.2
2020 Revolving Credit Agreement | Beyond6 | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense	0.0	0.2	0.1	0.2
11.5% Senior Secured Notes | Beyond6 | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense	0.0	0.8	0.3	1.6
Amortization of deferred financing costs and original issuance discount	$ 0.0	$ 0.1	$ 0.0	$ 0.2