NOTE 4. GOODWILL AND INTANGIBLE ASSETS

Goodwill represents the excess of the purchase price paid over the fair value of the net assets acquired in business combinations. Goodwill is not amortized but is tested for impairment at least annually. When evaluating whether goodwill is impaired, the Operating Company performs a qualitative assessment to determine if it is more likely than not that the fair value of a reporting unit is less than its carrying amount. The Operating Company would then recognize an impairment charge for the amount by which carrying amount exceeds the reporting unit's estimated fair value; however, goodwill would not be reduced below zero.

The Operating Company tests for impairment of goodwill annually in the fourth quarter or when management of the Operating Company deems that a triggering event has occurred. There were no impairments to goodwill during the three months ended March 31, 2019 and 2018. For three months ended March 31, 2019, the Operating Company recognized approximately $3.5 million in goodwill related to a business acquisition. The goodwill generated from the business acquisition is primarily related to the value placed on the expected business synergies. See "Note 12—Business Acquisition."

Identified intangible assets consisted of the following at the dates indicated below:

Amortization expense for the three months ended March 31, 2019 and 2018 was approximately $327,000 and $187,000, respectively.