Leases (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Components of Lease Expense

The components of lease expense for the periods presented below were as follows:

	Year Ended December 31,
	2021		2020		2019
	(Dollars in millions)
Operating lease cost:
Operating leases	$	19.8	$	28.8	$	43.3
Short-term leases	15.5		39.1		49.7
Variable leases	2.7		4.6		19.1
Sublease income	(1.9)		(2.3)		(2.6)
Total operating lease cost	$	36.1	$	70.2	$	109.5
Finance lease cost:
Amortization of right-of-use assets	$	5.9	$	3.5	$	15.3
Interest on lease liabilities	2.7		0.8		1.5
Total finance lease cost	$	8.6	$	4.3	$	16.8

Schedule of Supplemental Balance Sheet Information Related to Leases

Supplemental balance sheet information related to leases at December 31, 2021 and 2020 was as follows:

	December 31,
	2021			2020
	(Dollars in millions)
Operating leases:
Operating lease right-of-use assets	$	35.5		$	49.9
Accounts payable and accrued expenses	$	16.4		$	24.5
Operating lease liabilities, less current portion	27.2			42.1
Total operating lease liabilities	$	43.6		$	66.6
Finance leases:
Property, plant, equipment and mine development	$	32.2		$	20.4
Accumulated depreciation	(7.4)			(2.5)
Property, plant, equipment and mine development, net	$	24.8		$	17.9
Current portion of long-term debt	$	15.3		$	21.5
Long-term debt, less current portion	14.0			5.8
Total finance lease liabilities	$	29.3		$	27.3
Weighted average remaining lease term (years)
Operating leases	3.0
Finance leases	6.7
Weighted average discount rate
Operating leases	6.9		%
Finance leases	8.5		%

Schedule of Supplemental Cash Flow Information Related to Leases

Supplemental cash flow information related to leases for the periods presented below was as follows:

	Year Ended December 31,
	2021		2020		2019
	(Dollars in millions)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$	24.3	$	35.1	$	51.0
Operating cash flows for finance leases	3.8		0.8		1.5
Financing cash flows for finance leases	8.2		8.9		29.6
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	7.1		16.5		16.6
Finance leases	24.4		1.6		1.6

Lessee, Operating Lease, Liability, Maturity

The Company's leases have remaining lease terms ranging from 1 year to 20.0 years, and may include options to extend the terms, as applicable. The contractual maturities of lease liabilities were as follows:

Period Ending December 31,	Operating Leases		Finance Leases
	(Dollars in millions)
2022	$	18.9	$	11.4
2023	16.9		5.9
2024	6.0		4.9
2025	3.4		4.8
2026	3.5		2.4
2027 and thereafter	0.3		7.2
Total lease payments	49.0		36.6
Less imputed interest	(5.4)		(7.3)
Total lease liabilities	$	43.6	$	29.3

Finance Lease, Liability, Maturity

The Company's leases have remaining lease terms ranging from 1 year to 20.0 years, and may include options to extend the terms, as applicable. The contractual maturities of lease liabilities were as follows:

Period Ending December 31,	Operating Leases		Finance Leases
	(Dollars in millions)
2022	$	18.9	$	11.4
2023	16.9		5.9
2024	6.0		4.9
2025	3.4		4.8
2026	3.5		2.4
2027 and thereafter	0.3		7.2
Total lease payments	49.0		36.6
Less imputed interest	(5.4)		(7.3)
Total lease liabilities	$	43.6	$	29.3