Investment Securities (Tables)

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of investment securities available-for-sale

The following table shows investment securities available-for-sale.

(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
March 31, 2024
U.S. Treasury and Federal agencies securities	$	958,300	$	13	$	(55,428)	$	902,885
U.S. States and political subdivisions securities	92,875		223		(5,449)		87,649
Mortgage-backed securities — Federal agencies	667,973		64		(82,900)		585,137
Corporate debt securities	7,044		—		(64)		6,980
Foreign government and other securities	600		—		(7)		593
Total debt securities available-for-sale	$	1,726,792	$	300	$	(143,848)	$	1,583,244
December 31, 2023
U.S. Treasury and Federal agencies securities	$	979,530	$	178	$	(56,842)	$	922,866
U.S. States and political subdivisions securities	97,522		508		(5,466)		92,564
Mortgage-backed securities — Federal agencies	676,257		476		(78,481)		598,252
Corporate debt securities	8,448		—		(119)		8,329
Foreign government and other securities	600		—		(11)		589
Total debt securities available-for-sale	$	1,762,357	$	1,162	$	(140,919)	$	1,622,600

Schedule of contractual maturities of investments in debt securities available-for-sale

The following table shows the contractual maturities of investments in debt securities available-for-sale at March 31, 2024. Expected maturities will differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

(Dollars in thousands)	Amortized Cost		Fair Value
Due in one year or less	$	298,957	$	292,127
Due after one year through five years	727,883		674,372
Due after five years through ten years	13,151		12,729
Due after ten years	18,828		18,879
Mortgage-backed securities	667,973		585,137
Total debt securities available-for-sale	$	1,726,792	$	1,583,244

Schedule of gross unrealized losses and fair value by investment category and age

The following table summarizes gross unrealized losses and fair value by investment category and age. At March 31, 2024, the Company’s available-for-sale securities portfolio consisted of 661 securities, 606 of which were in an unrealized loss position.

	Less than 12 Months				12 months or Longer				Total
(Dollars in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
March 31, 2024
U.S. Treasury and Federal agencies securities	$	8,812	$	(84)	$	883,797	$	(55,344)	$	892,609	$	(55,428)
U.S. States and political subdivisions securities	5,194		(114)		64,560		(5,335)		69,754		(5,449)
Mortgage-backed securities - Federal agencies	19,900		(73)		537,697		(82,827)		557,597		(82,900)
Corporate debt securities	—		—		6,980		(64)		6,980		(64)
Foreign government and other securities	—		—		593		(7)		593		(7)
Total debt securities available-for-sale	$	33,906	$	(271)	$	1,493,627	$	(143,577)	$	1,527,533	$	(143,848)
December 31, 2023
U.S. Treasury and Federal agencies securities	$	—	$	—	$	913,417	$	(56,842)	$	913,417	$	(56,842)
U.S. States and political subdivisions securities	1,251		(2)		69,747		(5,464)		70,998		(5,466)
Mortgage-backed securities - Federal agencies	8,553		(98)		550,748		(78,383)		559,301		(78,481)
Corporate debt securities	—		—		8,329		(119)		8,329		(119)
Foreign government and other securities	—		—		589		(11)		589		(11)
Total debt securities available-for-sale	$	9,804	$	(100)	$	1,542,830	$	(140,819)	$	1,552,634	$	(140,919)

Schedule of gross realized gains and losses from securities available-for-sale portfolio

The following table shows the gross realized gains and losses from the available-for-sale debt securities portfolio. Realized gains and losses of all securities are computed using the specific identification cost basis.

	Three Months Ended March 31,
(Dollars in thousands)	2024		2023
Gross realized gains	$	—	$	1,286
Gross realized losses	—		(1,330)
Net realized losses	$	—	$	(44)