Financial Instruments and Other Guarantees - Narratives (Details) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Apr. 14, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Nov. 06, 2020 USD ($)
Guarantee Obligations [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 237.2			$ 237.2
Cumulative Collateral	557.8
Net loss on early debt extinguishment	2.0	$ 2.3		8.8	$ 25.8
Interest expense	13.3	37.6		31.7	77.0
Restricted Cash	731.4			731.4				$ 110.3
Difference between penal sum of all surety bonds and amount of collateral posted in favor of surety providers	533.6			$ 533.6
Letter of Credit
Guarantee Obligations [Line Items]
Proceeds from Issuance of Debt			$ 324.0
Line of Credit Facility, Increase (Decrease), Net	(65.0)
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage				6.00%
Line of Credit Facility, Commitment Fee Percentage				0.50%
Collateralized Letter of Credit Agreement
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	168.2			$ 168.2
Line of credit facility, maximum borrowing capacity	$ 250.0			$ 250.0
Cash Collateral, Percentage of the aggregate amount of letters of credit outstanding	103.00%			103.00%
Cash-collateralized Letters of Credit	$ 173.2			$ 173.2
Stated interest rate	0.75%			0.75%
Surety Trust Account
Guarantee Obligations [Line Items]
Restricted Cash	$ 558.2			$ 558.2			$ 566.3	$ 0.0
Accounts Receivable Securitization Program
Guarantee Obligations [Line Items]
Line of Credit Facility, Previous Maximum Borrowing Capacity	175.0			175.0
Line of credit facility, maximum borrowing capacity	225.0			225.0
Accounts Receivable Securitization Program | Secured debt
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	117.8			$ 117.8
Basis spread on variable rate				2.10%
Maximum
Guarantee Obligations [Line Items]
Debt Instrument, Collateral Amount						$ 721.8
Maximum | Collateralized Letter of Credit Agreement
Guarantee Obligations [Line Items]
Transaction support agreements, additional collateral demands	5.0			$ 5.0
Surety Bond
Guarantee Obligations [Line Items]
Debt Instrument, Transaction Support Agreements, Additional Collateral Posted	140.5			140.5
Debt Instrument, Transaction Support Agreement, Additional Collateral Held	$ 15.0			$ 15.0
Surety Agreement Liquidity Covenant, Amount						$ 400.0
Debt instrument, transaction support agreements, fair value of second liens on mining equipment									$ 200.0
Surety Bond | Maximum
Guarantee Obligations [Line Items]
Net Leverage Ratio						1.5
Surety Bond | Minimum
Guarantee Obligations [Line Items]
Net Leverage Ratio						1.0
Senior Notes | 3.250% Convertible Senior Notes due March 2028 (2028 Convertible Notes)
Guarantee Obligations [Line Items]
Debt Instrument, Funded, Percent						50.00%
Stated interest rate	3.25%			3.25%
Secured debt | Accounts Receivable Securitization Program
Guarantee Obligations [Line Items]
Outstanding borrowings	$ 0.0			$ 0.0
Accounts Receivable from Securitization	34.8			34.8
Interest expense	$ 0.8	$ 0.9		$ 1.9	$ 1.8