Discontinued Operations - Interest and Amortization (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense	$ 12.8	$ 17.9	$ 46.6	$ 56.2
Revolving Credit Agreement | GMSL | 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 | GMSL | 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	0.3	0.1	0.5
Amortization of deferred financing costs and original issuance discount	0.0	0.1	0.0	0.1
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	2.4
Amortization of deferred financing costs and original issuance discount	$ 0.0	$ 0.1	$ 0.0	$ 0.3