The following table presents the changes in the carrying amount of goodwill since its inception through March 31, 2020:


					Specialty
(in thousands)	Civil			Building	Contractors		Total
Gross goodwill	$	492,074	$	424,724	$	156,193	$	1,072,991
Accumulated impairment		(286,931)		(424,724)		(156,193)		(867,848)
Balance as of December 31, 2019		205,143		—		—		205,143
Current year activity		—		—		—		—
Balance as of March 31, 2020	$	205,143	$	—	$	—	$	205,143

The Company tests the goodwill allocated to its reporting units for impairment annually on October 1, or more frequently if events or circumstances indicate it is more likely than not that the fair value of a reporting unit is less than its carrying amount. The Company performed its annual impairment test in the fourth quarter of 2019 using a weighted-average of an income and a market approach. These approaches utilize various valuation assumptions, and small changes to the assumptions could have a significant impact on the concluded fair value. Based on this assessment, the Company concluded goodwill was not impaired since the estimated fair value of the Civil reporting unit exceeded its carrying value. In addition, the Company determined that no triggering events occurred and no circumstances changed since the date of our annual impairment test that would more likely than not reduce the fair value of the Civil reporting unit below its carrying amount.

During the first quarter of 2020, the novel coronavirus (“COVID-19”) pandemic, as well as the actions taken to contain and mitigate its public health effects, caused disruptions in domestic and global economies and financial markets. The vast majority of the Company’s projects, especially in its Civil reporting unit, have been designated as essential business, which allows the Company to continue its work on those projects. As such, the Company’s and its Civil reporting unit’s operations were not significantly impacted during the three months ended March 31, 2020. However, due to the fluidity of the pandemic, uncertainties as to its scope and duration, and ongoing changes in the way that governments, businesses and individuals react and respond to the COVID-19 pandemic, the Company is unable at this time to accurately predict the pandemic’s future impact on the Company’s business, financial condition or performance. Among other things, governments could prohibit the continuation of certain projects that to date have been designated as “essential” or could impose health, safety and other operational requirements on such projects that could result in delays to or suspensions of such projects. In addition, employees and contractors working on such projects could be unable or unwilling to continue working on them, perhaps for extended periods. The COVID-19 pandemic also could negatively affect the ability of counterparties or joint venture partners to make required payments on a timely basis or at all.

The Company will continue to monitor events and circumstances for changes that indicate the Civil reporting unit goodwill would need to be reevaluated for impairment during future interim periods prior to the annual impairment test. These future events and

circumstances include, but are not limited to, changes in the overall financial performance of the Civil reporting unit, impacts to our business as a result of the COVID-19 pandemic, as well as other quantitative and qualitative factors which could indicate potential triggering events for possible impairment.


	As of March 31, 2020								Weighted
					Accumulated				Average
				Accumulated	Impairment		Carrying		Amortization
(in thousands)	Cost			Amortization	Charge		Value		Period
Trade names (non-amortizable)	$	117,600	$	—	$	(67,190)	$	50,410	Indefinite
Trade names (amortizable)		74,350		(21,889)		(23,232)		29,229	20 years
Contractor license		6,000		—		(6,000)		—	N/A
Customer relationships		39,800		(21,311)		(16,645)		1,844	12 years
Construction contract backlog		149,290		(81,315)		—		67,975	3 years
Total	$	387,040	$	(124,515)	$	(113,067)	$	149,458



	As of December 31, 2019								Weighted
					Accumulated				Average
				Accumulated	Impairment		Carrying		Amortization
(in thousands)	Cost			Amortization	Charge		Value		Period
Trade names (non-amortizable)	$	117,600	$	—	$	(67,190)	$	50,410	Indefinite
Trade names (amortizable)		74,350		(21,267)		(23,232)		29,851	20 years
Contractor license		6,000		—		(6,000)		—	N/A
Customer relationships		39,800		(21,048)		(16,645)		2,107	12 years
Construction contract backlog		149,290		(76,388)		—		72,902	3 years
Total	$	387,040	$	(118,703)	$	(113,067)	$	155,270

Amortization expense for each of the quarters ended March 31, 2020 and 2019 was $5.8 million and $0.9 million, respectively. As of March 31, 2020, amortization expense is estimated to be $25.6 million for the remainder of 2020, $26.4 million in 2021, $24.6 million in 2022 and $2.5 million per year for the years 2023 through 2025.

The Company performed an annual impairment assessment of its non-amortizable trade names in the fourth quarter of 2019 using a qualitative approach to determine whether conditions existed to indicate that it is more likely than not that the fair value of trade names is less than their carrying values. Based on this assessment, the Company concluded that it was more likely than not that the fair value of the non-amortizable trade names was greater than their carrying values, and therefore a quantitative analysis was not required. In addition, no triggering events occurred and no circumstances changed since the date of our annual impairment test that would indicate any additional impairment of the Company’s non-amortizable trade names.