Other changes included in the above table include minor adjustments for the allocation of certain acquisitions still under measurement. For additional information regarding changes to goodwill resulting from acquisitions, see Note 16, Business Combinations.

We test goodwill for impairment annually during the fourth quarter of our fiscal year or earlier if there is an impairment indicator. We anticipate that the

COVID-19

pandemic could continue to have an impact on our customers and the homebuilding industry in general, as it could result in further business interruptions (government-mandated or otherwise) and could affect, among other factors, employment levels, consumer spending and consumer confidence, which could decrease demand for homes, adversely affecting our business. As such, we considered whether impairment indicators arose through the date of filing of this Quarterly Report on Form

10-Q

for our goodwill, long-lived assets and other intangible assets and concluded that no such factors exist. While we ultimately concluded that our goodwill, long-lived assets and other intangibles assets were not impaired as of June 30, 2020, we will continue to assess impairment indicators related to the impact of the

COVID-19

pandemic on our business. Accumulated impairment losses included within the above table were incurred over multiple periods, with the latest impairment charge being recorded during the year ended December 31, 2010.

Intangibles, net

The following table provides the gross carrying amount, accumulated amortization and net book value for each major class of intangibles (in thousands):


	As of June 30,						As of December 31,
	2020						2019
	Gross Carrying Amount		Accumulated Amortization		Net Book Value		Gross Carrying Amount		Accumulated Amortization		Net Book Value
Amortized intangibles:
Customer relationships	$	173,115	$	78,784	$	94,331	$	169,334	$	69,388	$	99,946
Covenants not-to-compete		17,389		12,088		5,301		16,959		10,617		6,342
Trademarks and tradenames		71,543		24,908		46,635		69,718		22,609		47,109
Backlog		15,004		14,154		850		14,080		13,915		165

	$	277,051	$	129,934	$	147,117	$	270,091	$	116,529	$	153,562

The gross carrying amount of intangibles increased approximately $7.0 million during the six months ended June 30, 2020 primarily due to business combinations. For more information, see Note 16, Business Combinations. Remaining estimated aggregate annual amortization expense is as follows (amounts, in thousands, are for the fiscal year ended):


Remainder of 2020	$	13,268
2021		25,573
2022		24,162
2023		21,251
2024		17,736
Thereafter		45,127