Goodwill and Other Intangible Assets

Goodwill

The carrying amounts of goodwill, by operating segment, for the years ended December 31, 2019 and 2018 were as follows:



	(In thousands)
	Electronic Systems			Structural Systems		Consolidated Ducommun
Gross goodwill	$	199,157		$	18,622	$	217,779
Accumulated goodwill impairment	(81,722		)	—		(81,722		)
Balance at December 31, 2018	117,435			18,622		136,057
Goodwill from acquisition during the period	—			34,860		34,860
Balance at December 31, 2019	$	117,435		$	53,482	$	170,917

We perform our annual goodwill impairment test as of the first day of the fourth quarter. See Note 1.

We acquired Certified Thermoplastics Co., LLC (“CTP”) in April 2018 and recorded goodwill of $18.6 million in our Structural Systems segment. Since a goodwill impairment analysis is required to be performed within one year of the acquisition date or sooner upon a triggering event, we performed a Step One goodwill impairment analysis as of April 2019 for our Structural Systems segment, which is also our reporting unit. The fair value of our Structural Systems segment exceeded its carrying value by 85% and thus, was not deemed impaired.

On October 8, 2019, we acquired 100.0% of the outstanding equity interests of Nobles for a purchase price of $77.0 million, net of cash acquired. We allocated the gross purchase price of $77.3 million to the assets acquired and liabilities assumed at estimated fair values. The excess of the purchase over the aggregate fair values was recorded as goodwill within the Structural Systems reporting unit. See Note 3.

In April 2018, we acquired 100.0% of the outstanding equity interests of CTP for a purchase price of $30.7 million, net of cash acquired. We allocated the gross purchase price of $30.8 million to the assets acquired and liabilities assumed at estimated fair values. The excess of the purchase over the aggregate fair values was recorded as goodwill within the Structural Systems reporting unit. See Note 3.

Other intangible assets are related to acquisitions, including Nobles, and recorded at fair value at the time of the acquisition. Other intangible assets with finite lives are generally amortized on the straight-line method over periods ranging from 10 to 18 years. Intangible assets are as follows:



		(In thousands)
		December 31, 2019						December 31, 2018
	Wtd. Avg Life (Yrs)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Finite-lived assets
Customer relationships	17	$	221,900	$	88,838	$	133,062	$	187,200	$	77,824	$	109,376
Trade names and trademarks	14	5,500		450		5,050		2,500		193		2,307
Contract renewal	14	1,845		1,757		88		1,845		1,625		220
Technology	15	400		238		162		400		211		189
Total		$	229,645	$	91,283	$	138,362	$	191,945	$	79,853	$	112,092

The carrying amount of other intangible assets by operating segment as of December 31, 2019 and 2018 was as follows:



	(In thousands)
	December 31, 2019						December 31, 2018
	Gross		Accumulated Amortization		Net Carrying Value		Gross		Accumulated Amortization		Net Carrying Value
Other intangible assets
Electronic Systems	$	164,545	$	71,527	$	93,018	$	164,545	$	62,108	$	102,437
Structural Systems	65,100		19,756		45,344		27,400		17,745		9,655
Total	$	229,645	$	91,283	$	138,362	$	191,945	$	79,853	$	112,092

Amortization expense of other intangible assets was $11.4 million, $10.7 million and $9.3 million for the years ended December 31, 2019, 2018 and 2017, respectively. Future amortization expense by operating segment is expected to be as follows:



	(In thousands)
	Electronic Systems		Structural Systems		Consolidated Ducommun
2020	$	9,348	$	3,719	$	13,067
2021	9,287		3,614		12,901
2022	9,288		3,553		12,841
2023	9,287		3,495		12,782
2024	9,288		3,260		12,548
Thereafter	46,520		27,703		74,223
	$	93,018	$	45,344	$	138,362