Intangibles (Net of Amortization) and Goodwill

The net carrying amount of intangibles and goodwill was $138 million at September 30, 2018 and $144 million at December 31, 2017. The gross carrying amount and accumulated amortization of each type of intangible asset and goodwill are presented in the table below.



	September 30, 2018				December 31, 2017
(in thousands)	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Amortizing intangible assets
Formulas and technology	$	9,600	$	2,708	$	12,339	$	3,280
Contract	2,000		350		2,000		200
Customer bases	14,240		8,214		15,759		5,140
Trademarks and trade names	0		0		1,531		1,213
Goodwill	122,965				122,541
	$	148,805	$	11,272	$	154,170	$	9,833

All of the intangibles relate to the petroleum additives segment. The change in the gross carrying amount between December 31, 2017 and September 30, 2018 is due to disposal of certain intangible assets, an immaterial adjustment to goodwill related to AMSA, and foreign currency fluctuation. See Note 2 for more information on the AMSA acquisition. There is no accumulated goodwill impairment.

Amortization expense was (in thousands):



Third quarter ended September 30, 2018	$	1,470
Nine months ended September 30, 2018	5,944
Third quarter ended September 30, 2017	928
Nine months ended September 30, 2017	1,364

Estimated amortization expense for the remainder of 2018, as well as estimated annual amortization expense related to our intangible assets for the next five years, is expected to be (in thousands):



2018	$	1,467
2019	4,207
2020	2,907
2021	2,156
2022	1,423
2023	907

We amortize contracts over 10 years; customer bases over 4 to 20 years; and formulas and technology over 3 to 6 years.