Business Combinations, Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2023

Business Combinations Goodwill And Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The following table presents the changes in the carrying value of our goodwill (in millions of dollars):

	As of December 31,
	2023			2022
Gross carrying value1:
Beginning balance	$	57.7		$	57.7
Warrick impairment		—			(20.5	)
Ending balance		57.7			37.2
Accumulated impairment loss1		(38.9	)		(18.4	)
Net carrying value	$	18.8		$	18.8

1.The gross carrying value and accumulated impairment loss excludes $25.2 million of goodwill recorded in conjunction with our acquisition of IMT.

Schedule of Gross Carrying Amount and Accumulated Amortization By Major Intangible Asset Class

The following table presents the gross carrying amount and accumulated amortization by major intangible asset class (in millions of dollars, except amortization periods):

	Weighted- Average Amortization Period (in years)		Gross Amount		Accumulated Amortization			Intangible Assets, Net
As of December 31, 2023
Customer relationships		19	$	68.1	$	(26.1	)	$	42.0
Trade name		10		2.4		(1.2	)		1.2
Non-compete agreement		5		5.4		(5.4	)		—
Favorable lease contracts		120		7.0		(0.2	)		6.8
Total			$	82.9	$	(32.9	)	$	50.0
As of December 31, 2022
Customer relationships		19	$	68.1	$	(21.9	)	$	46.2
Trade name		10		2.4		(1.0	)		1.4
Non-compete agreement		5		5.4		(4.6	)		0.8
Favorable lease contracts		120		7.0		(0.1	)		6.9
Total			$	82.9	$	(27.6	)	$	55.3

Schedule of Expected Amortization of Intangible Assets

The following table presents the expected amortization of intangible assets for each of the next five calendar years and thereafter as of December 31, 2023 (in millions of dollars):

2024	$	4.5
2025		4.5
2026		4.5
2027		4.5
2028		4.4
Thereafter		27.6
Total	$	50.0