Goodwill & Other Intangible Assets

Goodwill

Changes in the carrying amount of goodwill by reportable business segment for the years ended December 31, 2019 and 2018 were as follows (in thousands):



				Business
	Workforce			Transformation
	Excellence			Services			Total
Net book value at
January 1, 2018
Goodwill	$	114,814		$	45,438		$	160,252
Accumulated impairment losses	(9,050		)	(6,367		)	(15,417		)
Total	105,764			39,071			144,835
2018 Activity:
Acquisitions	21,613			14,033			35,646
Foreign currency translation	(3,459		)	(898		)	(4,357		)
Net book value at
December 31, 2018
Goodwill	132,968			58,573			191,541
Accumulated impairment losses	(9,050		)	(6,367		)	(15,417		)
Total	123,918			52,206			176,124
2019 Activity:
Purchase accounting adjustments	—			1,327			1,327
Divestitures	(7,681		)	—			(7,681		)
Foreign currency translation	1,776			17			1,793
Net book value at
December 31, 2019
Goodwill	127,063			59,917			186,980
Accumulated impairment losses	(9,050		)	(6,367		)	(15,417		)
Total	$	118,013		$	53,550		$	171,563

Intangible Assets Subject to Amortization

Intangible assets with finite lives are subject to amortization over their estimated useful lives. The primary assets included in this category and their respective balances were as follows (in thousands):



December 31, 2019
	Gross Carrying		Accumulated			Net Carrying
	Amount		Amortization			Amount
Customer relationships	$	22,348	$	(7,473	)	$	14,875
Intellectual property and other	3,915		(2,446		)	1,469
	$	26,263	$	(9,919	)	$	16,344

December 31, 2018
Customer relationships	$	26,524	$	(8,547	)	$	17,977
Intellectual property and other	4,936		(1,980		)	2,956
	$	31,460	$	(10,527	)	$	20,933

Amortization expense for intangible assets was $5.0 million, $4.6 million and $4.0 million for the years ended December 31, 2019, 2018 and 2017, respectively. Estimated future amortization expense for intangible assets included in our consolidated balance sheet as of December 31, 2019 is as follows (in thousands):



Fiscal year ending:
2020	$	3,908
2021	3,290
2022	2,086
2023	1,852
2024	1,852
Thereafter	3,356
Total	$	16,344

As of December 31, 2019, our intangible assets with definite lives had a weighted average remaining useful life of 5.7 years. We have no amortizable intangible assets with indefinite useful lives.