Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2024

Summary of Significant Accounting Policies

Schedule of allowance for credit losses

The activity in the allowance for credit losses was as follows (in millions):

	December 31,
	2024		2023		2022
Beginning balance	$	1.2	$	1.3	$	2.0
Provision		(0.1)		(0.1)		(0.7)
Write-offs, net		—		—		—
Ending balance	$	1.1	$	1.2	$	1.3

Schedule of inventories

Inventories consist of the following (in millions):

	December 31, 2024						December 31, 2023
			Supply and						Supply and
	Titled		Offtake				Titled		Offtake
	Inventory		Agreements (1)		Total		Inventory		Agreements (1)		Total
Raw materials	$	45.3	$	29.7	$	75.0	$	61.6	$	27.6	$	89.2
Work in process		63.8		33.7		97.5		72.3		36.7		109.0
Finished goods		160.3		83.5		243.8		162.1		79.1		241.2
	$	269.4	$	146.9	$	416.3	$	296.0	$	143.4	$	439.4

(1) Amounts represent LIFO value and do not necessarily represent the value at which the inventory was sold. Please read Note 7 — “Inventory Financing Agreements” for further information.

Schedule of property, plant and equipment

Property, plant and equipment, including depreciable lives, consisted of the following (in millions):

	December 31,
	2024		2023
Land	$	10.2	$	8.9
Buildings and improvements (10 to 40 years)		41.6		40.4
Machinery and equipment (10 to 20 years)		2,503.7		2,460.0
Furniture, fixtures and software (5 to 10 years)		47.5		47.1
Assets under finance leases (1 to 14 years) (1)		8.3		7.4
Construction-in-progress		42.0		39.5
		2,653.3		2,603.3
Less accumulated depreciation		(1,214.5)		(1,097.0)
	$	1,438.8	$	1,506.3

(1) Assets under finance leases consist of buildings and machinery and equipment. As of December 31, 2024 and 2023, finance lease assets are recorded net of accumulated amortization of $5.8 million and $5.0 million, respectively.