7. Goodwill and Intangible Assets

Goodwill represents the excess of the purchase price of an acquired business over the estimated fair values of the underlying net tangible and intangible assets. Goodwill consisted of the following:

	Amount
Balance at January 1, 2018	$	166,678
Measurement period adjustment		(549	)
Balance at June 30, 2018	$	166,129

Goodwill is allocated to the Company’s one reportable segment, which is its only reporting unit. During the six months ended June 30, 2018, the Company recorded measurement period adjustments to the preliminary purchase price allocations of the Blue Tree Acquisition and inthinc Acquisition of $393 and $156, respectively.

The Company’s intangible assets consisted of the following:

		June 30, 2018							December 31, 2017
	Useful life			Accumulated							Accumulated
	(years)	Cost		amortization			Net		Cost		amortization			Net
Customer lists	5 - 15	$	113,357	$	(34,654	)	$	78,703	$	113,357	$	(29,451	)	$	83,906
Patents and technology	5 - 10		23,424		(9,325	)		14,099		23,424		(8,080	)		15,344
Trade names and trademarks	1 - 2		3,004		(2,974	)		30		3,003		(2,914	)		89
		$	139,785	$	(46,953	)	$	92,832	$	139,784	$	(40,445	)	$	99,339

At June 30, 2018, the weighted-average amortization period for the intangible assets was 10.5 years. At June 30, 2018, the weighted-average amortization periods for customer lists, patents and technology and trade names and trademarks were 11.0, 9.3 and 1.2 years, respectively.

Amortization expense was $3,227 and $2,689 for the quarters ended June 30, 2018 and 2017, respectively. Amortization expense was $6,508 and $5,381 for the six months ended June 30, 2018 and 2017, respectively.

Estimated future amortization expense for intangible assets is as follows:

	Amount
2018 (remaining)	$	6,586
2019		12,860
2020		12,554
2021		12,143
2022		11,687
2023		11,438
Thereafter		25,564
	$	92,832