Goodwill represents the excess of the cost of an acquired business over the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed in a business combination. At both December 31, 2024 and 2023, we had $922.4 million of goodwill recorded in our Packaging segment, which represents the entire goodwill balance reported on our Consolidated Balance Sheets. We did not recognize any adjustments to goodwill during the years ended December 31, 2024 and 2023.

Intangible assets are primarily comprised of customer relationships and trademarks and trade names. The weighted average useful life, gross carrying amount, and accumulated amortization of our intangible assets were as follows (dollars in millions):


	As of December 31, 2024						As of December 31, 2023
	Weighted Average Remaining Useful Life (in Years)		Gross Carrying Amount		Accumulated Amortization		Weighted Average Remaining Useful Life (in Years)		Gross Carrying Amount		Accumulated Amortization
Customer relationships		6.6	$	546.0	$	362.4		7.4	$	546.0	$	326.9
Trademarks and trade names		6.0		41.3		33.0		6.5		41.3		30.9
Other		1.9		4.4		4.4		2.9		4.4		4.3
Total intangible assets (excluding goodwill)		6.6	$	591.7	$	399.8		7.3	$	591.7	$	362.1

Amortization expense was $37.7 million, $38.3 million, and $39.1 million for the years ended December 31, 2024, 2023, and 2022, respectively. Estimated amortization expense of intangible assets over the next five years is expected to approximate $37.6 million (2025), $37.5 million (2026), $34.7 million (2027), $27.1 million (2028) and $13.0 million (2029).

We test goodwill for impairment annually in the fourth quarter or sooner if events or changes in circumstances indicate that the carrying value of the asset may exceed fair value. Additionally, when we experience changes to our business or operating environment, we evaluate the remaining useful lives and recoverability of our finite-lived purchased intangible assets to determine whether any adjustments to the useful lives or impairment are necessary. We completed our annual qualitative assessment in the fourth quarter, and there was no indication of goodwill or intangible asset impairment.