Investment securities (Tables)

9 Months Ended

Sep. 30, 2020

Investments, Debt and Equity Securities [Abstract]

Summary 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 September 30, 2020 and December 31, 2019: 

	September 30, 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	$	—	$	(6)	$	—	$	1,994
Mortgage-backed securities - residential	723,333		15,093		(320)		—		738,106
Mortgage-backed securities - commercial	20,478		1,376		—		—		21,854
Municipals, tax exempt	359,761		15,813		(694)		—		374,880
Treasury securities	21,482		218		—		—		21,700
Corporate securities	1,999		3		(15)		—		1,987
Total	$	1,129,053	$	32,503	$	(1,035)	$	—	$	1,160,521

	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
Municipals, tax exempt	181,178		8,287		(230)		189,235
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.

	September 30,				December 31,
	2020				2019
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	18,861	$	19,009	$	1,148	$	1,152
Due in one to five years	29,353		29,811		11,553		11,676
Due in five to ten years	30,513		31,676		18,287		18,887
Due in over ten years	306,515		320,065		158,616		165,990
	385,242		400,561		189,604		197,705
Mortgage-backed securities - residential	723,333		738,106		474,144		477,312
Mortgage-backed securities - commercial	20,478		21,854		12,957		13,364
Total debt securities	$	1,129,053	$	1,160,521	$	676,705	$	688,381

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

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Proceeds from sales	$	28,257	$	22,740	$	28,257	$	24,498
Proceeds from maturities, prepayments and calls	67,886		28,694		140,246		78,861
Gross realized gains	563		1		563		7
Gross realized losses	39		76		39		83

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses for which an allowance for credit losses has not been recorded at September 30, 2020 and December 31, 2019, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	September 30, 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	$	1,994	$	(6)	$	—	$	—	$	1,994	$	(6)
Mortgage-backed securities - residential	107,236		(320)		—		—		107,236		(320)
Municipals, tax exempt	56,923		(694)		—		—		56,923		(694)
Corporate securities	985		(15)		—		—		985		(15)
Total	$	167,138	$	(1,035)	$	—	$	—	$	167,138	$	(1,035)

	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)
Municipals, tax exempt	15,433		(230)		—		—		15,433		(230)
Total	$	63,074	$	(394)	$	175,730	$	(1,497)	$	238,804	$	(1,891)