Financial Instruments and Other Guarantees (Details) - USD ($) $ in Millions	Jun. 30, 2023	Apr. 14, 2023	Mar. 31, 2023	Dec. 31, 2022
Guarantee Obligations [Line Items]
Restricted Cash	$ 731.4			$ 110.3
Deposits Assets	194.0			77.1
Restricted cash and collateral	925.4			187.4
LC Facility
Guarantee Obligations [Line Items]
Deposits Assets	0.0			28.5
Surety Trust Account
Guarantee Obligations [Line Items]
Restricted Cash	558.2		$ 566.3	0.0
Collateralized letters of credit funding
Guarantee Obligations [Line Items]
Restricted Cash	173.2			110.3
Deposits with Regulatory Authorities
Guarantee Obligations [Line Items]
Deposits Assets	194.0			33.6
Deposits Held on Behalf of Surety
Guarantee Obligations [Line Items]
Deposits Assets	0.0			15.0
Asset Retirement Obligations
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	23.8			437.8
Surety Bonds and Letters of Credit Outstanding for Reclamation Support	1,142.8			1,687.9
Letters of Credit in Support of Surety Bonds	(23.8)			(431.7)
Total Obligations Supported, Net	1,119.0			1,256.2
Surety bonds amount	1,119.0			1,250.1
Asset Retirement and Other Obligations
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	117.8			569.6
Total Surety Bonds and Letters of Credit Outstanding	1,349.9			1,946.4
Total Letters of Credit in Support of Surety Bonds	(29.7)			(468.9)
Total Obligations Supported, Net	1,320.2			1,477.5
Surety bonds amount	1,232.1			1,376.8
Other Obligations
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	94.0			131.8
Surety Bonds and Letters of Credit Outstanding for Other Support	207.1			258.5
Letters of Credit in Support of Surety Bonds	(5.9)			(37.2)
Total Obligations Supported, Net	201.2			221.3
Surety bonds amount	$ 113.1			$ 126.7
LC Facility
Guarantee Obligations [Line Items]
Mandatory Repurchase, Percentage of Accreted Value	95.00%
Debt instrument, repurchase amount	$ 30.0	$ 30.0
Secured debt | Accounts Receivable Securitization Program
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	117.8
Collateralized Letter of Credit Agreement
Guarantee Obligations [Line Items]
Letters of credit outstanding, amount	$ 168.2