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 as of September 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 September 30, 2018 and December 31, 2017 are as follows:


	As of September 30, 2018								As of December 31, 2017
	Gross						Net		Gross						Net
	Carrying		Accumulated		Accumulated		Carrying		Carrying		Accumulated		Accumulated		Carrying
(in thousands)	Amount		Amortization		Impairment		Amount		Amount		Amortization		Impairment		Amount
Customer lists	$	30,563	$	(22,671)	$	—	$	7,892	$	36,439	$	(24,267)	$	—	$	12,172
Other intangible assets		14,996		(10,551)		—		4,445		15,820		(10,352)		—		5,468
Definite-lived intangible assets		45,559		(33,222)		—		12,337		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	$	54,629	$	(33,222)	$	(4,770)	$	16,637	$	61,329	$	(34,619)	$	(4,770)	$	21,940

Total intangible amortization expense was approximately $1.5 million and $2.3 million for the three months ended September 30, 2018 and 2017, respectively and $5.3 million and $7.2 million for the nine months ended September 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)	$	1,436
2019		3,762
2020		3,509
2021		927
2022		860
Thereafter		1,843
Total	$	12,337