Goodwill and Intangible Assets

The changes in the carrying amount of goodwill are as follows:



	Diversified Industrial Segment			Aerospace Systems Segment		Total
Balance June 30, 2016	$	2,804,403		$	98,634	$	2,903,037
Acquisitions	2,677,489			—		2,677,489
Divestitures	(22,618		)	—		(22,618		)
Foreign currency translation and other	28,962			8		28,970
Balance June 30, 2017	$	5,488,236		$	98,642	$	5,586,878
Acquisitions	37,489			—		37,489
Divestitures	(138,541		)	—		(138,541		)
Foreign currency translation and other	18,587			7		18,594
Balance June 30, 2018	$	5,405,771		$	98,649	$	5,504,420

Acquisitions represent the original goodwill allocation, purchase price adjustments and final adjustments to the purchase price allocation for the acquisitions during the measurement period subsequent to the applicable acquisition dates. The impact of the purchase price adjustments and final adjustments to the purchase price allocation on the Company's results of operations and financial position were immaterial. Divestitures primarily represent goodwill associated with the sale of a business in 2018 and a product line in 2017 (see Note 2 for further discussion).

The Company's annual impairment tests performed in 2018, 2017 and 2016 resulted in no impairment loss being recognized.

Intangible assets are amortized on a straight-line method over their legal or estimated useful lives. The gross carrying value and accumulated amortization for each major category of intangible asset at June 30 are as follows:



	2018				2017
	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Patents	$	265,423	$	117,440	$	254,049	$	100,860
Trademarks	546,905		227,580		553,691		200,413
Customer lists and other	2,482,079		933,867		2,566,983		765,966
Total	$	3,294,407	$	1,278,887	$	3,374,723	$	1,067,239

Total intangible asset amortization expense in 2018, 2017 and 2016 was $221,494, $145,128 and $108,019, respectively. Estimated intangible asset amortization expense for the five years ending June 30, 2019 through 2023 is $197,451, $187,040, $182,406, $176,495 and $168,961, respectively.

Intangible assets are evaluated for impairment whenever events or circumstances indicate that the undiscounted net cash flows to be generated by their use over their expected useful lives and eventual disposition may be less than their net carrying value. No such events or circumstances occurred in 2018, 2017 or 2016.