Operations and Significant Accounting Policies - Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Residual Value Guarantee, Description	Our largest operating lease is for the dragline at BNI Energy which includes a termination payment at the end of the lease term if we do not exercise our purchase option.
Operating Lease, Right-of-Use Asset	$ 12.7	$ 16.4
Operating Lease, Cost	6.3	6.7
Operating Lease, Payments	6.3	6.7
Operating Lease Liabilities, Current	3.2	4.8
Operating Lease Liabilities, Non-Current	9.3	11.6
Operating Lease, Liability	12.5	$ 16.4
Residual Value of Leased Asset	$ 3.0
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Non-Current Liabilities	Other Non-Current Liabilities
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Non-Current Assets	Other Non-Current Assets
Vehicles and Equipment [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	4 years	3 years
Operating Lease, Weighted Average Discount Rate, Percent	3.90%	3.80%
Land and Other [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	16 years	27 years
Operating Lease, Weighted Average Discount Rate, Percent	3.90%	4.50%