NOTE 6 – GOODWILL AND INTANGIBLES

Goodwill

The change in carrying amount of goodwill was as follows (in thousands):


	Goodwill (Gross)		Accumulated Impairment Losses			Goodwill (Net)
January 1, 2017	$	177,090	$	(70,004	)	$	107,086
Business combinations		47,727		—			47,727
Other		653		—			653

December 31, 2017		225,470		(70,004	)		155,466
Business combinations		17,023		—			17,023
Other		560		—			560

December 31, 2018	$	243,053	$	(70,004	)	$	173,049

Other changes included in the above table for the years ended December 31, 2018 and 2017 include minor adjustments for the allocation of certain acquisitions still under measurement as well as several immaterial tuck-in acquisitions. For additional information regarding changes to goodwill resulting from acquisitions, see Note 15, Business Combinations.

At October 1, 2018, our measurement date, we performed a qualitative analysis that weighed all evidence of potential impairment, whether positive or negative, and determined that no factors existed that indicated an impairment of goodwill more likely than not existed. As such, no impairment of goodwill was recognized for the year ended December 31, 2018. In addition, no impairment of goodwill was recognized for the years ended December 31, 2017 or 2016.

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 December 31,
	2018						2017
	Gross				Net		Gross				Net
	Carrying		Accumulated		Book		Carrying		Accumulated		Book
	Amount		Amortization		Value		Amount		Amortization		Value
Amortized intangibles:
Customer relationships	$	148,635	$	52,514	$	96,121	$	121,015	$	38,651	$	82,364
Covenants not-to-compete		14,682		7,572		7,110		11,807		4,773		7,034
Trademarks and tradenames		64,432		18,256		46,176		58,136		14,076		44,060
Backlog		14,060		13,677		383		13,600		9,067		4,533

	$	241,809	$	92,019	$	149,790	$	204,558	$	66,567	$	137,991

There was no intangible asset impairment loss for the years ended December 31, 2018, 2017 and 2016.

The gross carrying amount of intangibles increased approximately $37.3 million and $77.7 million during the years ended December 31, 2018 and 2017, respectively. Intangibles associated with business combinations accounted for approximately $36.1 million and $76.8 million of the increases during the years ended December 31, 2018 and 2017, respectively, with the remaining changes due to other factors. For more information, see Note 15, Business Combinations. Amortization expense on intangible assets totaled approximately $25.4 million, $26.9 million and $11.3 million during the years ended December 31, 2018, 2017 and 2016, respectively. Remaining estimated aggregate annual amortization expense is as follows (in thousands):


2019	$	23,250
2020		22,318
2021		21,012
2022		20,094
2023		17,183
Thereafter		45,933