Other Intangible Assets and Goodwill

The following table sets forth information regarding the Company’s core deposit intangibles:



	At or for the Years ended
(Dollars in thousands)	December 31, 2018			December 31, 2017		December 31, 2016
Gross carrying value	$	62,977		21,649		21,943
Accumulated amortization	(13,735		)	(7,465	)	(9,596	)
Net carrying value	$	49,242		14,184		12,347
Aggregate amortization expense	$	6,270		2,494		2,970
Estimated amortization expense for the years ending December 31,
2019	$	6,768
2020	6,598
2021	6,407
2022	6,187
2023	5,711

Core deposit intangibles increased $41,328,000, $4,331,000 and $762,000 during 2018, 2017 and 2016, respectively, due to acquisitions. For additional information relating to acquisitions, see Note 22.

The following schedule discloses the changes in the carrying value of goodwill:



	Years ended
(Dollars in thousands)	December 31, 2018		December 31, 2017	December 31, 2016
Net carrying value at beginning of period	$	177,811	147,053	140,638
Acquisitions and adjustments	111,775		30,758	6,415
Net carrying value at end of period	$	289,586	177,811	147,053

The Company’s first step in evaluating goodwill for possible impairment is a control premium analysis. The analysis first calculates the market capitalization and then adjusts such value for a control premium range which results in an implied fair value. The control premium range is determined based on historical control premiums for acquisitions that are comparable to the Company and is obtained from an independent third party. The calculated implied fair value is then compared to the book value to determine whether the Company needs to proceed to step two of the goodwill impairment assessment. The Company performed its annual goodwill impairment test during the third quarter of 2018 and determined the fair value of the aggregated reporting units exceeded the carrying value, such that the Company’s goodwill was not considered impaired. In recognition there were no events or circumstances that occurred during the fourth quarter of 2018 that would more-likely-than-not reduce the fair value of a reporting unit below its carrying value, the Company did not perform interim testing at December 31, 2018. Changes in the economic environment, operations of the aggregated reporting units, or other factors could result in the decline in the fair value of the aggregated reporting units which could result in a goodwill impairment in the future. Accumulated impairment charges were $40,159,000 as of December 31, 2018 and 2017.