GOODWILL AND OTHER IDENTIFIABLE INTANGIBLE ASSETS, NET

Identifiable Intangible Assets, Net

Amortizable identifiable intangible assets, net as of September 30, 2018 and 2017 were comprised of the following (in thousands):



	September 30, 2018							September 30, 2017
	Gross carrying amount		Accum. amort.			Net		Gross carrying amount		Accum. amort.			Net
Purchased and core technology	$	58,102	$	(48,693	)	$	9,409	$	51,292	$	(46,304	)	$	4,988
License agreements	102		(46		)	56		18		(17		)	1
Patents and trademarks	15,701		(12,242		)	3,459		12,484		(11,280		)	1,204
Customer relationships	46,605		(21,049		)	25,556		21,914		(16,817		)	5,097
Non-compete agreements	600		(210		)	390		600		(90		)	510
Order backlog	1,800		(1,350		)	450		—		—			—
Total	$	122,910	$	(83,590	)	$	39,320	$	86,308	$	(74,508	)	$	11,800

Amortization expense is included in our consolidated statement of operations in cost of sales and general and administrative expense. Amortization expense in cost of sales includes amortization for purchased and core technology and certain patents and trademarks. Amortization expense for fiscal years 2018, 2017 and 2016 was as follows (in thousands):



Fiscal year	Total
2018	$	9,435
2017	$	2,597
2016	$	1,842

Estimated amortization expense for the next five years is as follows (in thousands):



Fiscal year	Total
2019	$	8,888
2020	$	8,118
2021	$	7,422
2022	$	6,554
2023	$	4,362

4. GOODWILL AND OTHER IDENTIFIABLE INTANGIBLE ASSETS, NET (CONTINUED)

Goodwill

The changes in the carrying amount of goodwill were (in thousands):



	Fiscal years ended September 30,
	2018			2017
Beginning balance, October 1	$	131,995		$	109,448
Acquisitions	23,216			21,465
Foreign currency translation adjustment	(676		)	1,082
Ending balance, September 30	$	154,535		$	131,995