The Corporation has goodwill from acquisitions which is deemed to be an indefinite intangible asset and is not amortized. In accordance with ASC Topic 350, goodwill is tested at least annually for impairment at the reporting unit level. The Corporation performs an annual test of goodwill for impairment during the fourth quarter of each year. The Corporation concluded there was no impairment of goodwill during 2018 through 2020.

The Corporation also has core deposit and customer-related intangibles and servicing rights, which are not deemed to have an indefinite life and therefore will continue to be amortized over their useful life using the present value of projected cash flows. The amortization of intangible assets for the years ended December 31, 2020, 2019 and 2018 was $4.5 million, $3.5 million and $3.4 million, respectively.

The Corporation also performs an annual test of other intangible assets for impairment during the fourth quarter of each year. The Corporation concluded there was no impairment of other intangible assets during 2018 through 2020.

Changes in the carrying amount of the Corporation's goodwill by business segment for the years ended December 31, 2020 and 2019 were as follows:


(Dollars in thousands)	Banking		Wealth Management		Insurance		Consolidated
Balance at December 31, 2018	$	138,476	$	15,434	$	18,649	$	172,559
Addition to goodwill from acquisitions	—		—		—		—
Balance at December 31, 2019	138,476		15,434		18,649		172,559
Addition to goodwill from acquisitions	—		—		—		—
Balance at December 31, 2020	$	138,476	$	15,434	$	18,649	$	172,559


	At December 31, 2020						At December 31, 2019
(Dollars in thousands)	Gross Carrying Amount		Accumulated Amortization (1)		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Amortized intangible assets:


Core deposit intangibles	$	6,788	$	4,787	$	2,001	$	6,788	$	4,026	$	2,762
Customer related intangibles	7,604		7,147		457		8,819		7,923		896
Servicing rights	22,354		15,946		6,408		19,160		12,534		6,626
Total amortized intangible assets	$	36,746	$	27,880	$	8,866	$	34,767	$	24,483	$	10,284

(1) Included within accumulated amortization is a valuation allowance of $87 thousand on mortgage servicing rights at December 31, 2020. There was no valuation allowance as of December 31, 2019.

The estimated aggregate amortization expense for core deposit and customer-related intangibles for each of the five succeeding fiscal years and thereafter follows:


(Dollars in thousands)
Year	Amount
2021	$	923
2022	666
2023	409
2024	267
2025	144
Thereafter	49
Total	$	2,458

The aggregate fair value of mortgage servicing rights was $6.7 million and $9.2 million at December 31, 2020 and 2019, respectively. The fair value of these rights was determined using a discount rate of 10.0% at December 31, 2020 and 2019.


	For the Years Ended December 31,
(Dollars in thousands)	2020		2019		2018
Beginning of period	$	6,626	$	6,768	$	6,573
Servicing rights capitalized	3,194		1,787		1,458

Amortization of servicing rights	(3,325)		(1,929)		(1,263)
Changes in valuation allowance	(87)		—		—
End of period	$	6,408	$	6,626	$	6,768
Loans serviced for others	$	1,200,742	$	1,080,905	$	1,031,506


	For the Years Ended December 31,
(Dollars in thousands)	2020		2019		2018
Valuation allowance, beginning of period	$	—	$	—	$	—
Additions	(87)		—		—


Valuation allowance, end of period	$	(87)	$	—	$	—

The estimated amortization expense of servicing rights for each of the five succeeding fiscal years and thereafter is as follows:


(Dollars in thousand)
Year	Amount
2021	$	1,675
2022	1,250
2023	931
2024	693
2025	427
Thereafter	1,432
Total	$	6,408