NOTE F — GOODWILL AND OTHER INTANGIBLE ASSETS

We assess goodwill and indefinite lived intangible assets for impairment annually on October 1st, and between annual tests if an event occurs, or circumstances change, that would more likely than not reduce the fair value of a reporting unit below its carrying value.

The carrying value of goodwill at June 30, 2018 and December 31, 2017 was $196.3 million and related to our Patient Care segment.

The balances related to intangible assets as of June 30, 2018 and December 31, 2017 are as follows:

	As of June 30, 2018										As of December 31, 2017
(in thousands)	Gross Carrying Amount		Accumulated Amortization			Accumulated Impairment			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Accumulated Impairment			Net Carrying Amount
Customer lists	$	30,976	$	(21,914	)	$	—		$	9,062	$	36,439	$	(24,267	)	$	—		$	12,172
Other intangible assets	15,005		(10,222		)	—			4,783		15,820		(10,352		)	—			5,468

Definite-lived intangible assets	45,981		(32,136		)	—			13,845		52,259		(34,619		)	—			17,640
Indefinite life - trade name	9,070		—			(4,770		)	4,300		9,070		—			(4,770		)	4,300

Total other intangible assets	$	55,051	$	(32,136	)	$	(4,770	)	$	18,145	$	61,329	$	(34,619	)	$	(4,770	)	$	21,940

Total intangible amortization expense was approximately $1.8 million and $2.4 million for the three months ended June 30, 2018 and 2017, respectively and $3.8 million and $4.9 million for the six months ended June 30, 2018 and 2017, respectively.

Estimated aggregate amortization expense for definite lived intangible assets for each of the next five years ended December 31st and thereafter is as follows:

(in thousands)
2018 (remainder of year)	$	2,944
2019	3,762
2020	3,509
2021	927
2022	860
Thereafter	1,843

Total	$	13,845