The change in the net carrying amount of goodwill for the six months ended July 2, 2022 by segment was as follows (in thousands):

	Steel Mills		Steel Products			Raw Materials			Total
Balance at December 31, 2021	$	613,175	$	1,439,874		$	774,295		$	2,827,344
Acquisitions		62,011		1,062,176			-			1,124,187
Other		-		-			(19,983	)		(19,983	)
Translation		-		(2,045	)		-			(2,045	)
Balance at July 2, 2022	$	675,186	$	2,500,005		$	754,312		$	3,929,503

Nucor completed its most recent annual goodwill impairment testing as of the first day of the fourth quarter of 2021 and concluded that as of such date there was no impairment of goodwill for any of its reporting units.

The annual assessment performed in 2021 for one of the Company’s reporting units, Rebar Fabrication, used forward-looking projections in future cash flows. The fair value of this reporting unit exceeded its carrying value by approximately 54% in the most recent assessment. If our assessment of the relevant facts and circumstances changes, including if the expected future performance of this reporting unit declines from the most recent assessment, non-cash impairment charges may be required. Total goodwill associated with the Rebar Fabrication reporting unit was $361.3 million as of July 2, 2022 ($363.0 million as of December 31, 2021). 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 were $40.9 million as of July 2, 2022 ($45.0 million as of December 31, 2021). There have been no triggering events requiring an interim assessment for impairment of the Rebar Fabrication reporting unit since the most recent annual goodwill impairment testing date.

Intangible assets with estimated useful lives of five to 25 years are amortized on a straight-line or accelerated basis and were comprised of the following as of July 2, 2022 and December 31, 2021 (in thousands):

	July 2, 2022				December 31, 2021
	Gross Amount		Accumulated Amortization		Gross Amount		Accumulated Amortization
Customer relationships	$	4,134,981	$	982,186	$	1,872,348	$	924,506
Trademarks and trade names		364,355		110,946		217,255		99,906
Other		108,446		85,501		105,522		66,954
	$	4,607,782	$	1,178,633	$	2,195,125	$	1,091,366

Intangible asset amortization expense in the second quarter of 2022 and 2021 was $45.9 million and $20.8 million, respectively, and $87.3 million and $41.9 million in the first six months of 2022 and 2021, respectively. Annual amortization expense is estimated to be $233.2 million in 2022; $232.7 million in 2023; $232.0 million in 2024; $231.0 million in 2025; and $228.0 million in 2026.