6. Goodwill and Intangible Assets

Goodwill represents the excess of net book value over the estimated fair value of net tangible and identifiable intangible assets of a reporting unit. Goodwill is tested for impairment annually or more often if impairment indicators are present at the reporting unit level. If events occur or circumstances change that would more likely than not reduce fair values of the reporting units below their carrying values, goodwill will be evaluated for impairment between annual tests. No triggering events indicating goodwill impairment occurred during the three months ended December 31, 2018. Please refer to Note 7, "Goodwill and Intangible Assets" to the Company's consolidated financial statements included in the 2018 Annual Report on Form 10-K for further information on the goodwill impairment testing performed during fiscal year 2018.

The components of the Company’s goodwill by operating segment at December 31, 2018 and September 30, 2018 are as follows (in thousands):


	Brooks
	Semiconductor
	Solutions		Brooks
	Group		Life Sciences		Other		Total
Gross goodwill, at September 30, 2018	$	636,907	$	207,913	$	26,014	$	870,834
Accumulated goodwill impairments		(588,944)		—		(26,014)		(614,958)
Goodwill, net of accumulated impairments, at September 30, 2018		47,963		207,913		—		255,876
Acquisitions and adjustments		(167)		234,816		—		234,649
Gross goodwill, at December 31, 2018		636,740		442,729		26,014		1,105,483
Accumulated goodwill impairments		(588,944)		—		(26,014)		(614,958)
Goodwill, net of accumulated impairments, at December 31, 2018	$	47,796	$	442,729	$	—	$	490,525

During the three months ended December 31, 2018, the Company recorded a goodwill increase of $234.6 million primarily related to the acquisition of GENEWIZ which represented the excess of the consideration transferred over the fair value of the net assets acquired. Please refer to the Note 5 "Acquisitions" for further information on this transaction.

The components of the Company’s identifiable intangible assets as of December 31, 2018 and September 30, 2018 are as follows (in thousands):


	December 31, 2018						September 30, 2018
			Accumulated		Net Book				Accumulated		Net Book
	Cost		Amortization		Value		Cost		Amortization		Value
Patents	$	5,302	$	4,401	$	901	$	5,302	$	4,325	$	977
Completed technology		88,475		30,790		57,685		44,829		28,934		15,895
Trademarks and trade names		25,316		3,444		21,872		6,298		2,953		3,345
Customer relationships		266,425		67,650		198,775		142,489		62,750		79,739
	$	385,518	$	106,285	$	279,233	$	198,918	$	98,962	$	99,956

Amortization expense for intangible assets was $7.8 million and $5.5 million, respectively, during the three months ended December 31, 2018 and 2017.

Estimated future amortization expense for the intangible assets for the remainder of fiscal year 2019, the subsequent four fiscal years and thereafter is as follows (in thousands):


Fiscal year ended September 30,
2019	$	26,976
2020		41,340
2021		37,547
2022		34,545
2023		31,589
Thereafter		107,236
	$	279,233