Note 6 - Intangible Assets

12 Months Ended

Dec. 31, 2018

Notes to Financial Statements

Goodwill and Intangible Assets Disclosure [Text Block]

6. Intangible Assets

Intangible assets consisted of the following (

in thousands

):

		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount	Weighted Average Amortization Period in Years
December 31, 2018
Customer relationships	$	156,790	$	(104,740	)	$	52,050	12.8
Trade names		16,246		(16,215	)		31	0.7
Intellectual property		21,700		(6,670	)		15,030	4.1
Restrictive covenants		263		(234	)		29	0.7
Total	$	194,999	$	(127,859	)	$	67,140

		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount	Weighted Average Amortization Period in Years
December 31, 2017
Customer relationships	$	159,290	$	(89,106	)	$	70,184	11.3
Trade names		16,246		(13,916	)		2,330	1.0
Intellectual property		21,700		(2,874	)		18,826	5.2
Restrictive covenants		263		(121	)		142	1.3
Total	$	197,499	$	(106,017	)	$	91,482

Amortization expense of intangible assets is expected to approximate the following (

in thousands

):

Year ending December 31,	Amortization
2019	$	9,195
2020		7,664
2021		7,197
2022		7,197
2023		4,822
Thereafter		31,065
Total	$	67,140

For the years ended

December 31, 2018,

2017

and

2016,

amortization expense related to intangible assets was

$24.3

million,

$22.6

million, and

$20.2

million, respectively. In addition, during the year ended

December 31, 2018,

some of the intangible assets became fully amortized.