Goodwill and Intangible Assets

6 Months Ended

Jun. 30, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill balances are presented below (in thousands):



	Carrying Amount
Balance as of December 31, 2018	$	148,845
Foreign currency translation adjustments	3,627
Balance as of June 30, 2019	$	152,472

Intangible assets consist of the following (in thousands):



	June 30,			December 31,
	2019			2018
Developed technology	$	140,800		$	114,395
Patents	66,530			57,180
Other	276			650
Intangible assets, gross	207,606			172,225
Less: accumulated amortization	(86,007		)	(71,643		)
Intangible assets, net	$	121,599		$	100,582

During the six months ended June 30, 2019, we acquired $36.2 million of intangible assets, comprising primarily $26.5 million of developed technology and $9.4 million in patents. The weighted-average useful lives for the developed technology and patents acquired during the six months ended June 30, 2019 was approximately 5.0 and 6.1 years, respectively.

During the six months ended June 30, 2018, apart from the business combinations described in Note 5, we also acquired $4.1 million of intangible assets in patents. The weighted-average useful life for the patents acquired during the six months ended June 30, 2018 was approximately 10.0 years.

Amortization expense for intangible assets for the three months ended June 30, 2019 and 2018 was approximately $8.0 million and $6.1 million, respectively, and for the six months ended June 30, 2019 and 2018 was approximately $15.1 million and $11.8 million, respectively.

The following table presents the estimated future amortization expense related to intangible assets held at June 30, 2019 (in thousands):



Years Ending December 31,
Remainder of 2019	$	18,056
2020	26,518
2021	24,346
2022	20,449
2023	14,607
Thereafter	17,623
Total future amortization expense	$	121,599