6.	GOODWILL AND OTHER INTANGIBLE ASSETS

The carrying amount of goodwill by reportable segment at December 31, 2018 and 2017 was $14.2 million for Trex Residential and $54.3 million for Trex Commercial.

Intangible assets consist of the following (in thousands):


	December 31, 2018			December 31, 2017
Intangible assets:
Customer backlog	$	4,000		$	4,000
Trade names and trademarks		900			900
Domain names		6,327			—

Total intangible assets		11,227			4,900

Accumulated amortization:
Customer backlog		(4,000	)		(1,666	)
Trade name and trademarks		(900	)		(376	)
Domain names		(285	)		—

Total accumulated amortization		(5,185	)		(2,042	)

Intantible assets, net	$	6,042		$	2,858

Intangible asset amounts were determined based on the estimated economics of the asset and are amortized over the estimated useful lives on a straight-line basis over 12 months for customer backlog and trade names and trademarks and 15 years for domain names, which approximates the pattern in which the economic benefits are expected to be received. In May 2018, the Company purchased certain domain names for $6.3 million. We evaluate the recoverability of intangible assets periodically and consider events or circumstances that may warrant revised estimates of useful lives or that may indicate an impairment. Intangible asset amortization expense for the years ended December 31, 2018 and December 31, 2017, was $3.1 million and $2.0 million, respectively.