(6) Goodwill and Other Intangible Assets

Goodwill and Indefinite Lived Intangible Assets

Changes in the carrying amount of goodwill are as follows:

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As presented in the accompanying consolidated balance sheets, trademarks are the other significant indefinite lived intangible asset. See the disclosure below for information related to the 2019 and 2017 impairments of the Company’s trademarks. Other fluctuations in the trademark balance from the prior year were due to the change in foreign exchange rates.

Intangible Assets subject to amortization

Intangible assets subject to amortization are comprised of the following:

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Intangible assets are being amortized generally on an accelerated basis as reflected in amortization expense and in the future amortization table below.

Amortization expense was $139 million, $137 million and $188 million for the years ended December 31, 2019, 2018 and 2017, respectively.

The estimated future amortization expense for the next five years related to intangible assets with definite lives as of December 31, 2019, assuming no subsequent impairment of the underlying assets, is as follows (amounts in millions):

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Impairments

Due to deteriorations in revenue, impairment losses of $288 million and $527 million were recorded during the years ended December 31, 2019 and December 31, 2017, respectively, related to trademarks.  The trademarks were related to the hotels, media & platform reporting unit in 2019 and the legacy hotels reporting unit in 2017, which is now included in the hotels, media & platform reporting unit.  The fair value of the trademarks was determined using the relief from royalty method.

Due to certain marketplace factors impacting Tripadvisor’s operating results, which led to a decline in Tripadvisor’s stock price, an impairment loss of $1,271 million was recorded during the year ended December 31, 2017 related to goodwill, related to the legacy hotel reporting unit, which is now included in the hotels, media & platform reporting unit. The fair values of the reporting units were determined using a combination of market multiples (market approach) and discounted cash flow (income approach) calculations (Level 3). As of December 31, 2019, accumulated goodwill impairment losses for Tripadvisor totaled $1,271 million.

There were no impairments recognized for the year ended December 31, 2018.