4. Goodwill and Other Intangible Assets

Changes in the Company’s goodwill balance for the three months ended March 31, 2019 are summarized in the table below (in thousands):



Balance at December 31, 2018	$	225,322
Adjustment related to prior year business combinations	2,708
Foreign currency translation adjustment	1,289
Balance at March 31, 2019	$	229,319

Net intangible assets include the estimated acquisition-date fair values of customer relationships, marketing-related assets, and developed technology that the Company recorded as part of its business acquisitions. The $2.7 million adjustment to Goodwill during the three months ended March 31, 2019 is primarily related to changes in the ASC 805 valuation of intangible assets in the prior year business combination of Adestra.

The following is a summary of the Company’s intangible assets, net (in thousands):



	Estimated Useful Life (Years)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
March 31, 2019:
Customer relationships	1-10	$	172,541	$	35,515	$	137,026
Trade name	1.5-10	5,867		3,455		2,412
Developed technology	4-7	48,526		17,945		30,581
Non-compete agreements	3	1,148		287		861
Total intangible assets		$	228,082	$	57,202	$	170,880



	Estimated Useful Life (Years)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
December 31, 2018:
Customer relationships	1-10	$	173,592	$	30,650	$	142,942
Trade name	1.5-10	6,113		3,334		2,779
Developed technology	4-7	48,943		16,049		32,894
Non-compete agreements	3	1,148		191		957
Total intangible assets		$	229,796	$	50,224	$	179,572

The Company periodically reviews the estimated useful lives of its identifiable intangible assets, taking into consideration any events or circumstances that might result in either a diminished fair value or revised useful life. There have been no indicators of impairment or change in useful life during the three months ended March 31, 2019 and March 31, 2018, respectively. Total amortization expense during the three months ended March 31, 2019 and March 31, 2018 was $6.8 million and $3.6 million, respectively.

Estimated annual amortization expense for the next five years and thereafter is as follows (in thousands):



	Amortization Expense
Year ending December 31:
Remainder of 2019	$	19,554
2020	24,458
2021	23,537
2022	21,226
2023	19,172
2024 and thereafter	62,933
Total	$	170,880