The following tables summarize the amortized cost, allowance for credit losses and fair value of the available-for-sale debt securities and the corresponding amounts of unrealized gains and losses recognized in accumulated other comprehensive income at December 31, 2020 and 2019:


	December 31, 2020
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Allowance for credit losses for investments		Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	2,000	$	3	$	—	$	—	$	2,003
Mortgage-backed securities - residential	760,099		14,040		(803)		—		773,336
Mortgage-backed securities - commercial	20,226		1,362		—		—		21,588
States and political subdivisions	336,543		19,806		(20)		—		356,329
U.S. Treasury securities	16,480		148		—		—		16,628
Corporate securities	2,500		17		(1)		—		2,516
Total	$	1,137,848	$	35,376	$	(824)	$	—	$	1,172,400


	December 31, 2019
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair Value
Investment Securities
Available-for-sale debt securities

Mortgage-backed securities - residential	$	474,144	$	4,829	$	(1,661)	$	477,312
Mortgage-backed securities - commercial	12,957		407		—		13,364
States and political subdivisions	181,178		8,287		(230)		189,235
U.S. Treasury securities	7,426		22		—		7,448
Corporate securities	1,000		22		—		1,022
Total	$	676,705	$	13,567	$	(1,891)	$	688,381

The components of amortized cost for debt securities on the consolidated balance sheets excludes accrued interest receivable since the Company elected to present accrued interest receivable separately on the consolidated balance sheets. As of December 31, 2020 and 2019, total accrued interest receivable on debt securities was $4,540 and $2,843, respectively.

As of December 31, 2020 and 2019, the Company had $4,591 and $3,295, respectively, in marketable equity securities recorded at fair value, respectively.

Securities pledged at December 31, 2020 and 2019 had carrying amounts of $804,821 and $373,674, respectively, and were pledged to secure a Federal Reserve Bank line of credit, public deposits and repurchase agreements.

There were no holdings of securities of any one issuer, other than the U.S. Government and its agencies, in an amount greater than 10% of shareholders' equity during any period presented.

At December 31, 2020 and December 31, 2019, there were no trade date payables that related to purchases settled after period end.

The amortized cost and fair value of debt securities by contractual maturity at December 31, 2020 and December 31, 2019 are shown below. Maturities may differ from contractual maturities in mortgage-backed securities because the mortgage underlying the security may be called or repaid without any penalties. Therefore, mortgage-backed securities are not included in the maturity categories in the following maturity summary.


	December 31,				December 31,
	2020				2019
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	35,486	$	35,662	$	1,148	$	1,152
Due in one to five years	24,278		24,684		11,553		11,676
Due in five to ten years	40,038		41,332		18,287		18,887
Due in over ten years	257,721		275,798		158,616		165,990
	357,523		377,476		189,604		197,705
Mortgage-backed securities - residential	760,099		773,336		474,144		477,312
Mortgage-backed securities - commercial	20,226		21,588		12,957		13,364
Total debt securities	$	1,137,848	$	1,172,400	$	676,705	$	688,381


	Year Ended December 31,
		2020		2019		2018
Proceeds from sales		$	146,494	$	24,498	$	2,742
Proceeds from maturities, prepayments and calls		220,549		113,018		73,066
Gross realized gains		1,606		7		9
Gross realized losses		271		98		44

Additionally, net unrealized gains on equity securities of $296 and $148 were recognized in the years ended December 31, 2020 and 2019, respectively.

The following tables show gross unrealized losses for which an allowance for credit losses has not been recorded at December 31, 2020 and December 31, 2019, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:


	December 31, 2020
	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
U.S. government agency securities	$	—	$	—	$	—	$	—	$	—	$	—
Mortgage-backed securities - residential	182,012		(803)		—		—		182,012		(803)
States and political subdivisions	3,184		(20)		—		—		3,184		(20)

Corporate securities	499		(1)		—		—		499		(1)
Total	$	185,695	$	(824)	$	—	$	—	$	185,695	$	(824)


	December 31, 2019
	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized loss

Mortgage-backed securities - residential	$	47,641	$	(164)	$	175,730	$	(1,497)	$	223,371	$	(1,661)
States and political subdivisions	15,433		(230)		—		—		15,433		(230)

Total	$	63,074	$	(394)	$	175,730	$	(1,497)	$	238,804	$	(1,891)

As of December 31, 2020 and December 31, 2019, the Company’s securities portfolio consisted of 514 and 365 securities, 16 and 58 of which were in an unrealized loss position, respectively.