Debt Obligations - Schedule of Debt (Details) - USD ($) $ in Millions		6 Months Ended
	Feb. 23, 2021	Jun. 30, 2021	Feb. 01, 2021	Dec. 31, 2020	Jun. 30, 2020
Debt Instrument [Line Items]
Obligations under finance leases		$ 0.2		$ 0.8
Total aggregate finance lease and debt payments		679.6			$ 576.6
Unamortized issuance discount, issuance premium, and deferred financing costs		(3.1)			(15.1)
Less: current portion of debt obligations		(70.2)		(433.6)	(433.6)
Debt obligations		606.3		$ 127.9	127.9
8.50% Senior Secured Notes, due 2026
Debt Instrument [Line Items]
Interest rate			100.00%
7.50% Convertible Senior Notes, due 2026
Debt Instrument [Line Items]
Interest rate			100.00%
Infrastructure
Debt Instrument [Line Items]
Obligations under finance leases		$ 0.1			0.2
Infrastructure | 4.00% Note due 2024
Debt Instrument [Line Items]
Interest rate		4.00%
Infrastructure | 8.00% Note due 2024
Debt Instrument [Line Items]
Interest rate		8.00%
Infrastructure | LIBOR | LIBOR plus 5.85% Note, due 2023 | DBM Global Credit Facilities
Debt Instrument [Line Items]
Basis spread on variable rate		5.85%
Infrastructure | LIBOR | LIBOR plus 5.85% Note, due 2023 | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		$ 0.0			71.6
Infrastructure | LIBOR | LIBOR plus 1.50% Line of Credit | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		$ 0.0			38.7
Infrastructure | LIBOR | LIBOR plus 1.50% Line of Credit | Real Estate Term Advance | DBM Global Credit Facilities | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		1.50%
Infrastructure | LIBOR | LIBOR plus 3.25% Note, due 2026 | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		$ 109.6			0.0
Infrastructure | LIBOR | LIBOR plus 3.25% Note, due 2026 | Real Estate Term Advance | DBM Global Credit Facilities | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		3.25%
Infrastructure | LIBOR | LIBOR plus 2.15% Line of Credit | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		$ 71.1			0.0
Infrastructure | LIBOR | LIBOR plus 2.15% Line of Credit | Real Estate Term Advance | DBM Global Credit Facilities | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		2.15%
Infrastructure | LIBOR | 4.00% Note due 2024 | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		$ 27.5			0.0
Infrastructure | LIBOR | 8.00% Note due 2024 | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		19.6			0.0
Infrastructure | LIBOR | Other, various maturity dates | Real Estate Term Advance
Debt Instrument [Line Items]
Outstanding debt		6.5			0.0
Spectrum
Debt Instrument [Line Items]
Obligations under finance leases		0.1			0.6
Spectrum | 8.50% Note due 2021
Debt Instrument [Line Items]
Outstanding debt		$ 19.3			19.3
Interest rate		8.50%
Spectrum | 10.50% Note due 2021
Debt Instrument [Line Items]
Outstanding debt		$ 32.9			32.9
Interest rate		10.50%
Spectrum | Other, various maturity dates
Debt Instrument [Line Items]
Outstanding debt		$ 2.9			2.9
Non-Operating Corporate | 11.50% Senior Secured Notes, due 2021
Debt Instrument [Line Items]
Outstanding debt		$ 0.0			340.4
Interest rate		11.50%
Non-Operating Corporate | 8.50% Senior Secured Notes, due 2026
Debt Instrument [Line Items]
Outstanding debt		$ 330.0			0.0
Interest rate		8.50%	8.50%
Non-Operating Corporate | 7.50% Convertible Senior Notes, due 2022
Debt Instrument [Line Items]
Outstanding debt		$ 3.2			55.0
Interest rate		7.50%	7.50%
Non-Operating Corporate | 7.50% Convertible Senior Notes, due 2026
Debt Instrument [Line Items]
Outstanding debt		$ 51.8			0.0
Interest rate		7.50%
Non-Operating Corporate | LIBOR plus 5.75% Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate	6.75%	5.75%
Outstanding debt		$ 5.0			$ 15.0
Non-Operating Corporate | LIBOR plus 5.75% Line of Credit | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	5.75%
Non-Operating Corporate | LIBOR plus 5.75% Line of Credit | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	6.75%