Goodwill and Intangible Assets, Net

Goodwill

Changes in the carrying amount of goodwill were as follows:



(In thousands)
Balance at December 31, 2016	$	43,052
Goodwill acquired during the period ⁽¹⁾	5,494
Foreign exchange effects	105
Balance at December 31, 2017	48,651
Foreign exchange effects	(166		)
Balance at December 31, 2018	$	48,485


⁽¹⁾	During 2017, we recognized $5.5 million of goodwill related to the Residential Control Systems, Inc. acquisition. Refer to Note 22 for further information about this acquisition.

We conducted annual goodwill impairment reviews on December 31, 2018, 2017, and 2016 utilizing significant unobservable inputs (level 3). Based on the analysis performed, we determined that our goodwill was not impaired.

Intangible Assets, Net

The components of intangible assets, net were as follows:



	December 31,
	2018							2017
(In thousands)	Gross ⁽¹⁾		Accumulated Amortization ⁽¹⁾			Net ⁽¹⁾		Gross ⁽¹⁾		Accumulated Amortization ⁽¹⁾			Net ⁽¹⁾
Distribution rights (10 years)	$	329	$	(188	)	$	141	$	344	$	(165	)	$	179
Patents (10 years)	14,560		(5,704		)	8,856		13,250		(5,310		)	7,940
Trademarks and trade names (10 years)	2,786		(1,900		)	886		2,786		(1,594		)	1,192
Developed and core technology (5-15 years)	12,560		(8,087		)	4,473		12,560		(6,071		)	6,489
Capitalized software development costs (2 years)	155		—			155		142		(77		)	65
Customer relationships (10-15 years)	32,534		(22,675		)	9,859		32,534		(19,395		)	13,139
Order backlog (1 year)	—		—			—		150		(113		)	37
Total intangible assets, net	$	62,924	$	(38,554	)	$	24,370	$	61,766	$	(32,725	)	$	29,041


⁽¹⁾	This table excludes the gross value of fully amortized intangible assets totaling $7.1 million and $6.0 million on December 31, 2018 and 2017, respectively.

Amortization expense is recorded in selling, general and administrative expenses, except amortization expense related to capitalized software development costs and order backlog, which is recorded in cost of sales. Amortization expense by statement of operations caption was as follows:



	Year Ended December 31,
(In thousands)	2018		2017		2016
Cost of sales	$	103	$	184	$	76
Selling, general and administrative expenses	7,081		6,772		6,198
Total amortization expense	$	7,184	$	6,956	$	6,274

Estimated future annual amortization expense related to our intangible assets at December 31, 2018, is as follows:



(In thousands)
2019	$	7,102
2020	5,938
2021	2,372
2022	2,259
2023	2,110
Thereafter	4,589
Total	$	24,370

The remaining weighted average amortization period of our intangible assets is 6.4 years.