INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2019

Our intangible assets are as follows:



	Year ended December 31,
(in thousands)	2019			2018
Definite-lived intangible assets
Customer relationships	$	24,440		$	24,764
Unpatented technology	14,917			15,098
Patented technology	2,598			2,616
Tradename	12,372			12,566
All other	9,225			9,728
Gross value of definite-lived intangible assets	63,552			64,772
Customer relationships amortization	(18,616		)	(17,219		)
Unpatented technology amortization	(5,245		)	(3,760		)
Patented technology amortization	(2,476		)	(2,348		)
Tradename amortization	(4,257		)	(3,672		)
All other amortization	(8,963		)	(8,285		)
Accumulated amortization	(39,557		)	(35,284		)
Net definite-lived intangible assets	$	23,995		$	29,488
Indefinite-lived intangible assets
Trademarks and trade names	$	1,305		$	1,305
Total intangible assets, net	$	25,300		$	30,793

The following summarizes the changes in the carrying amount of intangible assets:



	Year ended December 31,
(in thousands)	2019			2018
Balance at beginning of period	$	30,793		$	42,065
Amortization expense	(4,274		)	(6,715		)
Impairment expense	—			(2,521		)
Currency translation adjustments and other	(1,219		)	(2,036		)
Balance at end of the period	$	25,300		$	30,793

The following summarizes the changes in the carrying amount of intangible assets:



	Year ended December 31,
(in thousands)	2019			2018
Balance at beginning of period	$	30,793		$	42,065
Amortization expense	(4,274		)	(6,715		)
Impairment expense	—			(2,521		)
Currency translation adjustments and other	(1,219		)	(2,036		)
Balance at end of the period	$	25,300		$	30,793

Estimated future intangible asset amortization expense is as follows (in thousands):