As of June 30, 2020 and December 31, 2019 the carrying values of our indefinite lived intangible assets were as follows (in thousands):

We monitor the phases of development of our acquired in-process research and development projects, including the risks associated with further development and the amount and timing of benefits expected to be derived from the completed projects. Incremental costs associated with development are charged to expense as incurred. Capitalized costs are amortized over the estimated useful life of the developed asset once completed. Our in-process research and development projects are reviewed for impairment annually, or more frequently, if events or changes in circumstances indicate that the asset might be impaired.

Based on our experience with similar agreements, we believe that our acquired procurement contracts and agreements have indefinite useful lives, as we expect to continue to renew these contracts for the foreseeable future. We believe that our trademarks have indefinite useful lives as we currently anticipate that our trademarks will contribute to our cash flows indefinitely.

We evaluate our goodwill and non-amortizing intangible assets for impairment on an annual basis during the fourth quarter of the year, and, if necessary, during interim periods if factors indicate that an impairment review is warranted. As of June 30, 2020 we concluded that our assessment of current factors did not indicate that goodwill or non-amortizing intangible assets are more likely than not to be impaired. We will continue to evaluate the recoverability of these non-amortizing intangible assets in future periods as necessary.

As of June 30, 2020 and December 31, 2019 our entire goodwill balance was related to our Medical Devices segment.


	Medical Devices Segment
Balance as of December 31, 2019	$	186,697
Revaluation of goodwill denominated in foreign currency		(348)
Balance as of June 30, 2020	$	186,349

Definite Lived Intangible Assets

As of June 30, 2020 and December 31, 2019 the gross carrying values, accumulated amortization, and approximate amortization period of our definite lived intangible assets were as follows (in thousands):


	Gross Carrying		Accumulated		Amortization
June 30, 2020	Value		Amortization		Period
Acquired technology	$	139,867	$	28,932	11	–	22	Years
Customer lists and relationships		31,124		7,338	13	–	22	Years
Distribution and manufacturing rights and know-how		13,796		4,060	5	–	15	Years
Patents		3,800		3,098			17	Years
Other		2,452		753	4	–	10	Years

	Gross Carrying		Accumulated		Amortization
December 31, 2019	Value		Amortization		Period
Acquired technology	$	140,193	$	24,778	11	–	22	Years
Customer lists and relationships		31,131		6,581	13	–	22	Years
Distribution and manufacturing rights and know-how		13,826		3,005	5	–	15	Years
Patents		3,664		3,074			17	Years
Other		1,919		608	3	–	5	Years

Amortization Expense

The following is a summary of amortization expense as recorded in general, administrative, and marketing expenses on our Summary Consolidated Statement of Operations and Comprehensive (Income) Loss (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2020		2019		2020		2019
Amortization expense	$	3,000	$	2,557	$	6,033	$	5,136

As of June 30, 2020 scheduled amortization of intangible assets for the next five years is as follows (in thousands):


	Remainder
	of 2020		2021		2022		2023		2024		2025		Total
Amortization expense	$	6,169		12,440		11,894		11,368		11,141		9,147	$	62,159