Gross goodwill, accumulated impairments, and accumulated divestiture related write-offs were determined beginning January 1, 2002, when a change in accounting requirements resulted in goodwill being assessed for impairment rather than being amortized. Gross goodwill of $200.0 million with accumulated impairments and accumulated divestiture-related write-offs of $114.1 million and $85.9 million, respectively, were previously allocated to the non-strategic segment, resulting in $0 net goodwill allocated to the non-strategic segment as of September 30, 2020 and December 31, 2019. The regional banking and fixed income segments do not have any accumulated impairments or divestiture related write-offs.

On July 1, 2020, FHN completed its merger-of-equals transaction with IBERIABANK Corporation. In connection with the merger, FHN recorded a $532.2 million purchase accounting gain, based on preliminary fair value estimates.

On July 17, 2020, FHN completed its purchase of 30 branches from Truist Bank. In relation to the acquisition, FHN recorded $77.6 million in goodwill, based on preliminary fair value estimates. See Note 2 - Acquisitions and Divestitures for additional information regarding these transactions.

FHN performed the required annual goodwill impairment test as of October 1, 2019. The annual impairment test did not indicate impairment in any of FHN’s reporting units as of the testing date. Following the testing date, management evaluated the events and circumstances that could indicate that goodwill might be impaired and concluded that a subsequent interim test was not necessary. FHN is currently in the process of performing its annual impairment test as of October 1, 2020.

The following is a summary of goodwill by reportable segment included in the Consolidated Balance Sheets as of September 30, 2020 and December 31, 2019.


(Dollars in thousands)	Regional Banking		Fixed Income		Total
December 31, 2018	$	1,289,819	$	142,968	$	1,432,787
Additions	—		—		—
September 30, 2019	$	1,289,819	$	142,968	$	1,432,787

December 31, 2019	$	1,289,819	$	142,968	$	1,432,787
Additions	77,644		—		77,644
September 30, 2020	$	1,367,463	$	142,968	$	1,510,431

Intangible assets subject to amortization

In connection with the IBKC merger and the Truist branch acquisition, FHN recorded $206.7 million and $7.0 million of core deposit intangible assets, respectively. Core deposit intangible assets are subject to amortization over a ten years period. In connection with the IBKC merger, FHN recorded $14.0 million of customer relationship intangible assets, $10.3 million of purchased credit card intangible assets, and $6.8 million of title plant related to title company operations. The following table, which excludes fully amortized intangibles, presents other intangible assets included in the Consolidated Balance Sheets:


	September 30, 2020						December 31, 2019
(Dollars in thousands)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Value		Gross Carrying Amount		Accumulated Amortization		Net Carrying Value
Core deposit intangibles	$	370,850	$	(68,902)	$	301,948	$	157,150	$	(47,372)	$	109,778
Customer relationships	37,000		(7,037)		29,963		77,865		(60,150)		17,715
Other (a)	38,685		(4,896)		33,789		5,622		(2,915)		2,707
Total	$	446,535	$	(80,835)	$	365,700	$	240,637	$	(110,437)	$	130,200

(a)Includes noncompete covenants, purchased credit card intangible assets, and state banking licenses not subject to amortization.

Amortization expense was $14.6 million and $6.2 million for the three months ended September 30, 2020 and 2019, respectively and $25.2 million and $18.6 million for nine months ended September 30, 2020 and 2019, respectively. As of September 30, 2020 the estimated aggregated amortization expense is expected to be:


(Dollars in thousands)
Year	Amortization
Remainder of 2020	$	14,921
2021	55,943
2022	51,498
2023	47,859
2024	44,040
2025	37,145