Goodwill represents the excess of the consideration paid over the fair value of the net assets acquired or the excess of the fair value of the net liabilities assumed over the consideration received in a business combination. The 2019 acquisition of MidSouth resulted in goodwill of $63.4 million. The carrying amount of goodwill was $855.5 million at both December 31, 2020 and 2019. For additional information regarding changes to the Company’s carrying amount of goodwill, refer to Note 2 – Business Combination.

In the fourth quarter of 2020, the Company completed its annual test of impairment as of September 30, 2020 using multiple approaches to measure the fair value of the reporting unit and concluded there was no impairment. These methods included an income approach using the discounted net present value of estimated future cash flows and three market approaches using transaction or price-to-forward earnings multiples, price to tangible book value methodologies using the actual price paid in recent acquisition transactions for similar entities and a market capitalization approach using the Company’s stock price observed during the fourth quarter. The results from each of the approaches were weighted equally, with the valuation of the reporting unit approximately 17% in excess of net book value at September 30, 2020. Individually, no valuation method resulted in estimated fair value less than the Company’s carrying value.

Valuation techniques employed by the Company require significant assumptions. Depending upon the specific approach, assumptions are made regarding the economic environment, expected net interest margins, growth rates, discount rate used to present value future cash flows, control premiums, and price-to-forward earnings and price to-tangible-book-value multiples. Changes to any one of these assumptions could result in significantly different results. Changes in the amount and/or timing of the Company’s expected future cash flows or estimated growth rates, lack of improvement and/or further decline in the price of the Company’s common stock relative to our book value per share, and/or further deterioration in the economic environment beyond current estimates could result in an impairment charge to goodwill in future reporting periods.

The Company completed its annual impairment test of goodwill as of September 30, 2019 by performing a qualitative (“Step Zero”) assessment. The qualitative assessment involved the examination of changes in macroeconomic conditions, industry and market conditions, overall financial performance, cost factors and other relevant entity-specific events, including changes in management and other key personnel and changes in the share price of the Company’s common stock. As a result of the assessment, the Company concluded that its goodwill was not impaired.

No goodwill impairment charges were recognized during the years ended December 31, 2020, 2019 or 2018.

Identifiable intangible assets with finite lives are amortized over the periods benefited and are evaluated for impairment similar to other long-lived assets. The purchase and carrying values of intangible assets subject to amortization at December 31, 2020 and 2019 were as follows:

	December 31, 2020
	Purchase		Accumulated		Carrying
(in thousands)	Value		Amortization		Value
Core deposit intangibles	$	235,845	$	173,830	$	62,015
Credit card and trust relationships		49,962		25,085		24,877
Merchant processing relationships		10,000		10,000		—
	$	295,807	$	208,915	$	86,892

	December 31, 2019
	Purchase		Accumulated		Carrying
(in thousands)	Value		Amortization		Value
Core deposit intangibles	$	247,455	$	168,577	$	78,878
Credit card and trust relationships		49,962		22,448		27,514
Merchant processing relationships		10,000		9,585		415
	$	307,417	$	200,610	$	106,807

Aggregate amortization expense by category of finite lived intangible assets for the years ended December 31, 2020, 2019, and 2018 is as follows:

	Years Ended December 31,
(in thousands)	2020		2019		2018
Core deposit intangibles	$	16,864	$	17,132	$	18,566
Credit card and trust relationships		2,637		2,883		2,682
Merchant processing relationships		415		829		802
	$	19,916	$	20,844	$	22,050

At December 31, 2020, the weighted-average remaining life of core deposit intangibles was approximately 9 years, and the weighted-average remaining life of other identifiable intangibles was approximately 14 years.

The following table shows estimated amortization expense of other intangible assets at December 31, 2020 for the five succeeding years and all years thereafter, calculated based on current amortization schedules.

(in thousands)
2021	$	16,665
2022		14,033
2023		11,557
2024		9,413
2024		7,985
Thereafter		27,239
	$	86,892