Investment Securities (Tables)

9 Months Ended

Sep. 30, 2024

Investment 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
September 30, 2024:
U.S. Government agencies	$	147,271	$	—	$	(19,271)	$	128,000
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,333,263		—		(188,925)		1,144,338
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		419,838		—		(58,371)		361,467
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		349,860		—		(61,691)		288,169
Small Business Administration loan-backed securities		51,075		—		(9,303)		41,772
	$	2,301,307	$	—	$	(337,561)	$	1,963,746
December 31, 2023:
U.S. Government agencies	$	197,267	$	—	$	(24,607)	$	172,660
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,438,102		—		(227,312)		1,210,790
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		444,883		—		(68,139)		376,744
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		354,055		—		(71,327)		282,728
Small Business Administration loan-backed securities		53,133		—		(11,319)		41,814
	$	2,487,440	$	—	$	(402,704)	$	2,084,736

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
September 30, 2024:
U.S. Treasuries	$	2,684	$	1	$	—	$	2,685
U.S. Government agencies		191,177		—		(15,453)		175,724
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,702,457		491		(216,862)		1,486,086
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		574,447		49		(82,254)		492,242
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,215,415		2,545		(157,131)		1,060,829
State and municipal obligations		1,123,634		63		(134,394)		989,303
Small Business Administration loan-backed securities		363,885		57		(34,432)		329,510
Corporate securities		30,499		—		(2,515)		27,984
	$	5,204,198	$	3,206	$	(643,041)	$	4,564,363
December 31, 2023:
U.S. Treasuries	$	74,720	$	—	$	(830)	$	73,890
U.S. Government agencies		246,089		—		(21,383)		224,706
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,822,104		294		(264,092)		1,558,306
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		626,735		—		(99,313)		527,422
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,217,125		1,516		(194,471)		1,024,170
State and municipal obligations		1,129,750		2		(152,291)		977,461
Small Business Administration loan-backed securities		413,950		86		(42,350)		371,686
Corporate securities		30,533		—		(3,786)		26,747
	$	5,561,006	$	1,898	$	(778,516)	$	4,784,388

Schedule of amortized cost and carrying value of other investment securities

	Carrying
(Dollars in thousands)	Value
September 30, 2024:
Federal Home Loan Bank stock	$	32,336
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other investment securities		25,298
	$	211,458
December 31, 2023:
Federal Home Loan Bank stock	$	22,836
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other investment securities		15,383
	$	192,043

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	$	14,365	$	14,222	$	84,976	$	84,297
Due after one year through five years		36,471		33,648		341,428		327,521
Due after five years through ten years		444,858		393,780		1,217,855		1,084,899
Due after ten years		1,805,613		1,522,096		3,559,939		3,067,646
	$	2,301,307	$	1,963,746	$	5,204,198	$	4,564,363

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
September 30, 2024:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	19,271	$	128,000
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		188,925		1,144,338
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		58,371		361,467
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		61,691		288,169
Small Business Administration loan-backed securities		—		—		9,303		41,772
	$	—	$	—	$	337,561	$	1,963,746
Securities Available for Sale
U.S. Treasuries (1)	$	—	$	696	$	—	$	—
U.S. Government agencies		—		—		15,453		175,724
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		80		17,925		216,781		1,452,928
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		82,254		487,928
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		157,131		958,412
State and municipal obligations		1,259		17,464		133,136		960,941
Small Business Administration loan-backed securities		2		684		34,430		311,253
Corporate securities		—		—		2,515		27,984
	$	1,341	$	36,769	$	641,700	$	4,375,170
December 31, 2023:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	24,607	$	172,660
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		227,312		1,210,790
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		68,139		376,745
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		71,327		282,728
Small Business Administration loan-backed securities		—		—		11,319		41,814
	$	—	$	—	$	402,704	$	2,084,737
Securities Available for Sale
U.S. Treasuries	$	—	$	—	$	830	$	73,890
U.S. Government agencies		—		—		21,383		224,706
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		122		9,358		263,970		1,539,208
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		99,313		527,422
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		91		7,959		194,380		955,059
State and municipal obligations		177		6,340		152,114		967,305
Small Business Administration loan-backed securities		128		42,447		42,222		304,770
Corporate securities		18		480		3,768		26,267
	$	536	$	66,584	$	777,980	$	4,618,627

(1) The U.S. Treasury securities in a continuous unrealized losses position for less than twelve months at September 30, 2024, had a combined gross unrealized loss total of less than $1,000.

Schedule of trading securities

	September 30,		December 31,
(Dollars in thousands)	2024		2023
U.S. Government agencies	$	10,730	$	1,537
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		15,969		14,461
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		24,344		—
State and municipal obligations		26,347		14,620
Small Business Administration loan-backed securities		8,552		—
Other debt securities		1,161		703
	$	87,103	$	31,321

Summary of net losses on trading securities

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(Dollars in thousands)	2024		2023		2024		2023
Net gains (losses) on sales transaction	$	533	$	(76)	$	757	$	(116)
Net mark to mark (losses) gains		(167)		176		(478)		(25)
Net gains (losses) on trading securities	$	366	$	100	$	279	$	(141)