Investment securities (Tables)

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost of Securities and Fair Values

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

Schedule of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

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

Schedule of Sales and Other Dispositions of Available-for-Sale Securities

Sales and other dispositions of available-for-sale securities were as follows:

	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

Schedule of Gross Unrealized Losses

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)