Investment securities (Tables)

3 Months Ended

Mar. 31, 2022

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 March 31, 2022 and December 31, 2021:  

	March 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	$	41,015	$	—	$	(2,133)	$	—	$	38,882
Mortgage-backed securities - residential	1,320,205		616		(88,565)		—		1,232,256
Mortgage-backed securities - commercial	14,738		14		(445)		—		14,307
Municipal securities	318,587		3,594		(12,043)		—		310,138
U.S. Treasury securities	81,913		4		(1,744)		—		80,173
Corporate securities	8,000		4		(235)		—		7,769
Total	$	1,784,458	$	4,232	$	(105,165)	$	—	$	1,683,525

	December 31, 2021
	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	$	34,023	$	18	$	(171)	$	—	$	33,870
Mortgage-backed securities - residential	1,281,285		6,072		(17,985)		—		1,269,372
Mortgage-backed securities - commercial	15,024		272		(46)		—		15,250
Municipal securities	322,052		16,718		(160)		—		338,610
U.S. Treasury securities	14,914		—		(6)		—		14,908
Corporate securities	6,500		40		(25)		—		6,515
Total	$	1,673,798	$	23,120	$	(18,393)	$	—	$	1,678,525

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,
	2022				2021
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	19,614	$	19,602	$	21,851	$	21,884
Due in one to five years	121,436		118,438		54,847		55,307
Due in five to ten years	55,733		54,635		45,714		46,975
Due in over ten years	252,732		244,287		255,077		269,737
	449,515		436,962		377,489		393,903
Mortgage-backed securities - residential	1,320,205		1,232,256		1,281,285		1,269,372
Mortgage-backed securities - commercial	14,738		14,307		15,024		15,250
Total debt securities	$	1,784,458	$	1,683,525	$	1,673,798	$	1,678,525

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,
	2022		2021
Proceeds from sales	$	—	$	—
Proceeds from maturities, prepayments and calls	57,443		61,040
Gross realized gains	2		7
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, 2022 and December 31, 2021, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	March 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	$	38,882	$	(2,133)	$	—	$	—	$	38,882	$	(2,133)
Mortgage-backed securities - residential	961,993		(70,839)		175,988		(17,726)		1,137,981		(88,565)
Mortgage-backed securities - commercial	9,647		(445)		—		—		9,647		(445)
Municipal securities	192,546		(11,844)		1,030		(199)		193,576		(12,043)
U.S. Treasury securities	47,918		(1,744)		—		—		47,918		(1,744)
Corporate securities	6,896		(235)		—		—		6,896		(235)
Total	$	1,257,882	$	(87,240)	$	177,018	$	(17,925)	$	1,434,900	$	(105,165)

	December 31, 2021
	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	$	18,360	$	(171)	$	—	$	—	$	18,360	$	(171)
Mortgage-backed securities - residential	$	871,368	$	(14,295)	$	102,799	$	(3,690)	$	974,167	$	(17,985)
Mortgage-backed securities - commercial	7,946		(46)		—		—		7,946		(46)
Municipal securities	11,414		(160)		—		—		11,414		(160)
U.S. Treasury securities	14,908		(6)		—		—		14,908		(6)
Corporate securities	4,119		(25)		—		—		4,119		(25)
Total	$	928,115	$	(14,703)	$	102,799	$	(3,690)	$	1,030,914	$	(18,393)