The change in the net carrying amount of goodwill for the years ended December 31, 2022 and 2021 by segment is as follows:

	(in thousands)
	Steel		Steel			Raw
	Mills		Products			Materials			Total
Balance, December 31, 2020	$	612,470	$	887,625		$	729,577		$	2,229,672
Acquisitions		705		553,704			44,718			599,127
Translation		—		(1,455	)		—			(1,455	)
Balance, December 31, 2021		613,175		1,439,874			774,295			2,827,344
Acquisitions		62,011		1,087,906			—			1,149,917
Divestitures		—		—			(39,466	)		(39,466	)
Translation		—		(17,735	)		—			(17,735	)
Balance, December 31, 2022	$	675,186	$	2,510,045		$	734,829		$	3,920,060

Intangible assets with estimated useful lives of five to 25 years are amortized on a straight-line or accelerated basis and are comprised of the following:

	(in thousands)
	December 31, 2022				December 31, 2021
	Gross		Accumulated		Gross		Accumulated
	Amount		Amortization		Amount		Amortization
Customer relationships	$	4,174,724	$	1,087,834	$	1,872,348	$	924,506
Trademarks and trade names		364,106		142,363		217,255		99,906
Other		109,746		96,114		105,522		66,954
	$	4,648,576	$	1,326,311	$	2,195,125	$	1,091,366

Intangible asset amortization expense was $234.9 million in 2022 ($129.2 million in 2021 and $83.4 million in 2020). Annual amortization expense is estimated to be $234.8 million in 2023, $234.0 million in 2024, $233.0 million in 2025, $230.0 million in 2026 and $226.0 million in 2027.

The Company completed its annual goodwill impairment testing as of the first day of the fourth quarter for each of 2022, 2021 and 2020 and concluded that as of each such date there was no impairment of goodwill for any of its reporting units.

The annual assessment performed in 2022 for the Rebar Fabrication reporting unit used forward-looking projections and included continued positive future cash flows. The fair value of this reporting unit exceeded its carrying value by approximately 34 % in the most recent assessment. Although profitability fluctuates year-to-year, we currently expect the reporting unit to be profitable in 2023. If our assessment of the relevant facts and circumstances changes, or the actual performance of this reporting unit falls short of expected results, non-cash impairment charges may be required. Total goodwill associated with the Rebar Fabrication reporting unit as of December 31, 2022 was $347.6 million. An impairment of goodwill may also lead us to record an impairment of other intangible assets. Total finite-lived intangible assets associated with the Rebar Fabrication reporting unit as of December 31, 2022 was $36.3 million.

There are no significant historical accumulated impairment charges, by segment or in the aggregate, related to goodwill.