GOODWILL AND OTHER INTANGIBLE ASSETS

The following table presents the changes in the carrying amount of goodwill and other intangible assets during the year ended December 31, 2019 (in thousands):



	Goodwill		Other Intangible Assets			Total
Balances as of December 31, 2018	194,052		67,207			$	261,259
Translation adjustment	—		449			449
Amortization	—		(15,074		)	(15,074		)
Balances as of December 31, 2019	$	194,052	$	52,582		$	246,634

The following table presents the changes in the carrying amount of goodwill and other intangible assets during the year ended December 31, 2018 (in thousands):



	Goodwill		Other Intangible Assets			Total
Balances as of December 31, 2017	187,591		78,525			$	266,116
Translation adjustment	—		(917		)	(917		)
Acquisition of ASI	6,461		6,185			12,646
Amortization	—		(16,586		)	(16,586		)
Balances as of December 31, 2018	$	194,052	$	67,207		$	261,259

The following table presents the goodwill balance by reportable segment as of December 31, 2019 and 2018 (in thousands):



	As of December 31,
	2019		2018
Service Centers	$	160,934	$	160,934
Innovative Pumping Solutions	15,980		15,980
Supply Chain Services	17,138		17,138
Total	$	194,052	$	194,052

The following table presents a summary of amortization of other intangible assets ( in thousands):



	As of December 31, 2019							As of December 31, 2018
	Gross Carrying Amount		Accumulated Amortization			Carrying Amount, net		Gross Carrying Amount		Accumulated Amortization			Carrying Amount, net
Customer relationships	$	156,282	$	(103,796	)	$	52,486	$	168,255	$	(101,200	)	$	67,055
Non-compete agreements	285		(189		)	96		784		(632		)	152
Total	$	156,567	$	(103,985	)	$	52,582	$	169,039	$	(101,832	)	$	67,207

Gross carrying amounts as well as accumulated amortization are partially affected by the fluctuation of foreign currency rates. Other intangible assets are amortized according to estimated economic benefits over their estimated useful lives.

Customer relationships are amortized over their estimated useful lives. Amortization expense is recognized according to estimated economic benefits and was $15.1 million, $16.6 million, and $17.3 million for the years ended December 31, 2019, 2018, and 2017, respectively. The estimated future annual amortization of intangible assets for each of the next five years and thereafter are as follows (in thousands):



2020	$	11,611
2021	9,287
2022	7,974
2023	6,508
2024	4,886
Thereafter	12,316
Total	$	52,582

The weighted average remaining estimated life for customer relationships and non-compete agreements are 7.33 and 2.58, respectively.