v3.20.2
Goodwill and Intangible Assets
 6 Months Ended
Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]  
Goodwill and Intangible Assets Goodwill and Intangible Assets
Goodwill balances are presented below (in thousands):
Carrying Amount
Balance as of December 31, 2019$156,756  
Goodwill acquired54,635  
Foreign currency translation adjustments25  
Balance as of June 30, 2020$211,416  

Intangible assets consist of the following (in thousands):
 June 30, 2020December 31, 2019
Developed technology$212,533  $177,746  
Patents67,109  67,730  
Other3,594  3,594  
Intangible assets, gross283,236  249,070  
Less: accumulated amortization(119,379) (105,220) 
Intangible assets, net$163,857  $143,850  

During the six months ended June 30, 2020, apart from the business combinations described in Note 5, we acquired $7 million of intangible assets in developed technology. The weighted-average useful life for the developed technology acquired during the six months ended June 30, 2020 was approximately 5 years.

During the six months ended June 30, 2019, we acquired $36 million of intangible assets, comprising primarily $27 million of developed technology and $9 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 and 6 years, respectively.

Amortization expense for intangible assets for the three months ended June 30, 2020 and 2019 was $15 million and $8 million, respectively, and for the six months ended June 30, 2020 and 2019 was $25 million and $15 million, respectively.
The following table presents the estimated future amortization expense related to intangible assets held at June 30, 2020 (in thousands):
Years Ending December 31,
Remainder of 2020$20,883  
202140,684  
202236,547  
202331,396  
202426,228  
Thereafter8,119  
Total future amortization expense$163,857