Investment securities (Tables)

3 Months Ended

Mar. 31, 2023

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 loss at March 31, 2023 and December 31, 2022:  

	March 31, 2023
	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	$	45,176	$	—	$	(4,248)	$	—	$	40,928
Mortgage-backed securities - residential	1,197,702		—		(172,314)		—		1,025,388
Mortgage-backed securities - commercial	18,979		—		(1,256)		—		17,723
Municipal securities	295,010		967		(24,983)		—		270,994
U.S. Treasury securities	113,403		—		(4,580)		—		108,823
Corporate securities	8,000		—		(851)		—		7,149
Total	$	1,678,270	$	967	$	(208,232)	$	—	$	1,471,005

	December 31, 2022
	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	$	45,167	$	—	$	(5,105)	$	—	$	40,062
Mortgage-backed securities - residential	1,224,522		—		(190,329)		—		1,034,193
Mortgage-backed securities - commercial	19,209		—		(1,565)		—		17,644
Municipal securities	295,375		458		(31,413)		—		264,420
U.S. Treasury securities	113,301		—		(5,621)		—		107,680
Corporate securities	8,000		—		(813)		—		7,187
Total	$	1,705,574	$	458	$	(234,846)	$	—	$	1,471,186

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 summary.

	March 31,				December 31,
	2023				2022
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	34,965	$	34,270	$	4,277	$	4,225
Due in one to five years	138,189		130,585		161,556		152,181
Due in five to ten years	58,876		56,982		61,290		57,859
Due in over ten years	229,559		206,057		234,720		205,084
	461,589		427,894		461,843		419,349
Mortgage-backed securities - residential	1,197,702		1,025,388		1,224,522		1,034,193
Mortgage-backed securities - commercial	18,979		17,723		19,209		17,644
Total debt securities	$	1,678,270	$	1,471,005	$	1,705,574	$	1,471,186

Schedule 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 March 31,
	2023		2022
Proceeds from sales	$	—	$	—
Proceeds from maturities, prepayments and calls	26,827		57,443
Gross realized gains	—		2
Gross realized losses	—		—

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses for which an allowance for credit losses has not been recorded at March 31, 2023 and December 31, 2022, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	March 31, 2023
	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	$	4,014	$	(94)	$	36,913	$	(4,154)	$	40,927	$	(4,248)
Mortgage-backed securities - residential	101,194		(4,425)		924,189		(167,889)		1,025,383		(172,314)
Mortgage-backed securities - commercial	11,311		(740)		6,415		(516)		17,726		(1,256)
Municipal securities	43,100		(1,872)		161,743		(23,111)		204,843		(24,983)
U.S. Treasury securities	60,669		(1,276)		48,154		(3,304)		108,823		(4,580)
Corporate securities	946		(55)		6,281		(796)		7,227		(851)
Total	$	221,234	$	(8,462)	$	1,183,695	$	(199,770)	$	1,404,929	$	(208,232)

	December 31, 2022
	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	$	23,791	$	(2,802)	$	16,271	$	(2,303)	$	40,062	$	(5,105)
Mortgage-backed securities - residential	316,656		(32,470)		717,533		(157,859)		1,034,189		(190,329)
Mortgage-backed securities - commercial	11,104		(968)		6,541		(597)		17,645		(1,565)
Municipal securities	196,419		(26,811)		36,726		(4,602)		233,145		(31,413)
U.S. Treasury securities	94,248		(4,122)		13,434		(1,499)		107,682		(5,621)
Corporate securities	4,008		(492)		3,270		(321)		7,278		(813)
Total	$	646,226	$	(67,665)	$	793,775	$	(167,181)	$	1,440,001	$	(234,846)