Intangibles

The company's intangibles consist of the following (in thousands):



	March 31, 2018				December 31, 2017
	Historical Cost		Accumulated Amortization		Historical Cost		Accumulated Amortization
Customer lists	$	55,504	$	53,250	$	54,516	$	51,957
Trademarks	26,837		—		26,372		—
Developed technology	8,069		6,796		7,925		6,636
Patents	5,549		5,542		5,566		5,559
License agreements	1,173		1,173		1,187		1,187
Other	1,162		1,146		1,162		1,145
Intangibles	$	98,294	$	67,907	$	96,728	$	66,484

All the company’s intangible assets have been assigned definite lives and continue to be amortized over their useful lives, except for trademarks shown above, which have indefinite lives. The changes in intangible balances reflected on the balance sheet from December 31, 2017 to March 31, 2018 were the result of foreign currency translation and amortization.

The company evaluates the carrying value of definite-lived assets whenever events or circumstances indicate possible impairment. Definite-lived assets are determined to be impaired if the future un-discounted cash flows expected to be generated by the asset are less than the carrying value. Actual impairment amounts for definite-lived assets are then calculated using a discounted cash flow calculation. The company reviews indefinite-lived assets for impairment annually in the fourth quarter of each year and whenever events or circumstances indicate possible impairment. Any impairment amounts for indefinite-lived assets are calculated as the difference between the future discounted cash flows expected to be generated by the asset less than the carrying value for the asset.

Amortization expense related to intangibles was $418,000 in the first three months of 2018 and is estimated to be $1,677,000 in 2018, $1,348,000 in 2019, $198,000 in 2020, $198,000 in 2021, $198,000 in 2022 and $198,000 in 2023. Amortized intangibles are being amortized on a straight-line basis over remaining lives of 1 to 10 years with most of the intangibles being amortized over an average remaining life of approximately 4 years.