Securities (Tables)

3 Months Ended

Mar. 31, 2025

Securities

Schedule of amortized cost and fair value of investment securities held to maturity

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
(Dollars in thousands)	Cost		Gains		Losses		Value
March 31, 2025:
U.S. Government agencies	$	132,908	$	—	$	(20,361)	$	112,547
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,262,776		—		(214,924)		1,047,852
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		405,003		—		(63,798)		341,205
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		346,083		—		(66,345)		279,738
Small Business Administration loan-backed securities		49,210		—		(10,079)		39,131
	$	2,195,980	$	—	$	(375,507)	$	1,820,473
December 31, 2024:
U.S. Government agencies	$	147,272	$	—	$	(23,498)	$	123,774
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,297,543		—		(241,204)		1,056,339
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		411,721		—		(72,057)		339,664
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		348,338		—		(72,391)		275,947
Small Business Administration loan-backed securities		49,796		—		(10,993)		38,803
	$	2,254,670	$	—	$	(420,143)	$	1,834,527

Schedule of amortized cost and fair value of investment securities available for sale

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
(Dollars in thousands)	Cost		Gains		Losses		Value
March 31, 2025:
U.S. Treasuries	$	18,294	$	—	$	(1)	$	18,293
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,613,205		3,570		(169,659)		1,447,116
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		2,397,132		7,758		(57,756)		2,347,134
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		643,484		1,396		(84,246)		560,634
State and municipal obligations		1,085,891		22		(175,264)		910,649
Small Business Administration loan-backed securities		571,923		270		(29,640)		542,553
Corporate securities		28,498		—		(1,508)		26,990
	$	6,358,427	$	13,016	$	(518,074)	$	5,853,369
December 31, 2024:
U.S. Treasuries	$	10,654	$	2	$	—	$	10,656
U.S. Government agencies		169,207		—		(18,789)		150,418
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,659,851		97		(282,423)		1,377,525
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		557,288		19		(98,212)		459,095
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,234,573		562		(194,580)		1,040,555
State and municipal obligations		1,117,330		2		(171,609)		945,723
Small Business Administration loan-backed securities		351,814		19		(41,721)		310,112
Corporate securities		28,499		—		(1,990)		26,509
	$	5,129,216	$	701	$	(809,324)	$	4,320,593

Schedule of amortized cost and carrying value of other investment securities

	Carrying
(Dollars in thousands)	Value
March 31, 2025:
Federal Home Loan Bank stock	$	25,209
Federal Reserve Bank stock		232,474
Investment in unconsolidated subsidiaries		5,287
Other investment securities		82,725
	$	345,695
December 31, 2024:
Federal Home Loan Bank stock	$	18,087
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other investment securities		51,702
	$	223,613

Schedule of amortized cost and fair value of debt and equity securities by contractual maturity

	Securities				Securities
	Held to Maturity				Available for Sale
	Amortized		Fair		Amortized		Fair
(Dollars in thousands)	Cost		Value		Cost		Value
Due in one year or less	$	—	$	—	$	49,944	$	49,711
Due after one year through five years		56,378		51,887		202,653		198,349
Due after five years through ten years		409,257		356,482		738,102		679,180
Due after ten years		1,730,345		1,412,104		5,367,728		4,926,129
	$	2,195,980	$	1,820,473	$	6,358,427	$	5,853,369

Schedule of information with respect to sales of available-for-sale securities

	Three Months Ended March 31,
	2025
(Dollars in thousands)	Sales of Securities Acquired from Independent		Investment Securities Sales		Total
Sale proceeds	$	1,279,717	$	1,594,393	$	2,874,110
Gross realized gains		—		8,892		8,892
Gross realized losses		—		(237,703)		(237,703)
Net realized losses	$	—	$	(228,811)	$	(228,811)

Schedule of securities with gross unrealized losses, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position

	Less Than				Twelve Months
	Twelve Months				or More
	Gross Unrealized		Fair		Gross Unrealized		Fair
(Dollars in thousands)	Losses		Value		Losses		Value
March 31, 2025:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	20,361	$	112,547
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		214,924		1,047,852
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		63,798		341,205
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		66,345		279,738
Small Business Administration loan-backed securities		—		—		10,079		39,131
	$	—	$	—	$	375,507	$	1,820,473
Securities Available for Sale
U.S. Treasuries	$	1	$	18,294	$	—	$	—
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,037		158,905		168,622		863,252
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		1,294		908,932		56,462		318,887
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		224		26,921		84,022		417,171
State and municipal obligations		100		3,487		175,164		899,151
Small Business Administration loan-backed securities		376		278,043		29,264		227,796
Corporate securities		—		—		1,508		26,991
	$	3,032	$	1,394,582	$	515,042	$	2,753,248
December 31, 2024:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	23,498	$	123,774
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		241,204		1,056,339
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		72,057		339,664
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		72,391		275,947
Small Business Administration loan-backed securities		—		—		10,993		38,803
	$	—	$	—	$	420,143	$	1,834,527
Securities Available for Sale
U.S. Treasuries	$	—	$	—	$	—	$	—
U.S. Government agencies		—		—		18,789		150,418
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		294		14,341		282,129		1,350,268
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		98,212		454,908
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		792		53,342		193,788		918,338
State and municipal obligations		1,484		19,400		170,125		923,431
Small Business Administration loan-backed securities		24		6,747		41,697		289,786
Corporate securities		—		—		1,990		26,509
	$	2,594	$	93,830	$	806,730	$	4,113,658

Schedule of trading securities

	March 31,		December 31,
(Dollars in thousands)	2025		2024
U.S. Government agencies	$	5,573	$	15,002
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		26,500		14,803
Other residential mortgage issued or guaranteed by U.S. government
agencies or sponsored enterprises		3,890		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		19,345		14,419
State and municipal obligations		37,516		35,896
Small Business Administration loan-backed securities		14,577		22,571
Other debt securities		—		241
	$	107,401	$	102,932

Summary of net gains (losses) on trading securities

	Three Months Ended
	March 31,
(Dollars in thousands)	2025		2024
Net gains on sales transaction	$	362	$	54
Net unrealized gains		121		12
Net gains on trading securities	$	483	$	66