Note 15: Goodwill

Goodwill is recognized when the consideration paid for a business exceeds the fair value of the tangible and identifiable intangible assets acquired. Goodwill is allocated to reporting units for purposes of testing goodwill for impairment. There were no charges for goodwill impairment in the three month periods ended March 31, 2019 and 2018. Accumulated goodwill impairment losses amount to $252,664,000 in the Calcium segment.

We have four reportable segments organized around our principal product lines: Aggregates, Asphalt, Concrete and Calcium. Changes in the carrying amount of goodwill by reportable segment from December 31, 2018 to March 31, 2019 are summarized below:



in thousands	Aggregates	Asphalt	Concrete	Calcium	Total
Goodwill
Total as of December 31, 2018	$ 3,073,763	$ 91,633	$ 0	$ 0	$ 3,165,396
Goodwill of acquired businesses 1	(3,554)	0	0	0	(3,554)
Total as of March 31, 2019	$ 3,070,209	$ 91,633	$ 0	$ 0	$ 3,161,842


1	See Note 16 for a summary of prior year acquisitions.

We test goodwill for impairment on an annual basis or more frequently if events or circumstances change in a manner that would more likely than not reduce the fair value of a reporting unit below its carrying value. A decrease in the estimated fair value of one or more of our reporting units could result in the recognition of a material, noncash write-down of goodwill.