Securities (Tables)

12 Months Ended

Dec. 31, 2023

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
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
December 31, 2022:
U.S. Government agencies	$	197,262	$	—	$	(29,787)	$	167,475
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,591,646		—		(255,093)		1,336,553
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		474,660		—		(69,664)		404,996
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		362,586		—		(66,304)		296,282
Small Business Administration loan-backed securities		57,087		—		(12,225)		44,862
	$	2,683,241	$	—	$	(433,073)	$	2,250,168

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
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
December 31, 2022:
U.S. Treasuries	$	272,416	$	—	$	(6,778)	$	265,638
U.S. Government agencies		245,972		—		(26,884)		219,088
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,996,405		—		(298,052)		1,698,353
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		708,337		—		(107,292)		601,045
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,196,700		2,542		(198,844)		1,000,398
State and municipal obligations		1,269,525		1,210		(205,883)		1,064,852
Small Business Administration loan-backed securities		491,203		302		(46,695)		444,810
Corporate securities		35,583		—		(2,945)		32,638
	$	6,216,141	$	4,054	$	(893,373)	$	5,326,822

Schedule of amortized cost and carrying value of other investment securities

	Carrying
(Dollars in thousands)	Value
December 31, 2023:
Federal Home Loan Bank stock	$	22,836
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		15,383
	$	192,043
December 31, 2022:
Federal Home Loan Bank stock	$	15,085
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		10,808
	$	179,717

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	$	50,000	$	49,222	$	158,338	$	156,418
Due after one year through five years		50,955		46,440		267,073		254,908
Due after five years through ten years		480,806		414,831		1,343,076		1,165,142
Due after ten years		1,905,679		1,574,243		3,792,519		3,207,920
	$	2,487,440	$	2,084,736	$	5,561,006	$	4,784,388

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

	Year Ended December 31,
(Dollars in thousands)	2023		2022		2021
Securities Available for Sale:
Sale proceeds	$	129,614	$	482,028	$	151,314
Gross realized gains		1,335		103		750
Gross realized losses		(1,292)		(73)		(648)
Net realized gain	$	43	$	30	$	102

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
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
December 31, 2022:
Securities Held to Maturity
U.S. Government agencies	$	5,514	$	78,833	$	24,273	$	88,642
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		65,181		513,086		189,912		823,467
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		30,284		277,868		39,380		127,128
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		14,318		82,895		51,986		213,387
Small Business Administration loan-backed securities		—		—		12,225		44,862
	$	115,297	$	952,682	$	317,776	$	1,297,486
Securities Available for Sale
U.S. Treasuries	$	6,778	$	265,638	$	—	$	—
U.S. Government agencies		8,193		138,807		18,691		80,281
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		42,767		459,773		255,285		1,238,580
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		21,450		274,082		85,842		326,963
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		17,156		206,228		181,688		767,002
State and municipal obligations		97,084		616,631		108,799		391,848
Small Business Administration loan-backed securities		2,152		92,535		44,543		264,933
Corporate securities		2,209		28,374		736		4,264
	$	197,789	$	2,082,068	$	695,584	$	3,073,871

Schedule of trading securities

	December 31,		December 31,
(Dollars in thousands)	2023		2022
U.S. Government agencies	$	1,537	$	11,190
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		14,461		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		4,589
State and municipal obligations		14,620		13,993
Other debt securities		703		1,491
	$	31,321	$	31,263

Summary of net gains (losses) on trading securities

	Year Ended December 31,
(Dollars in thousands)	2023		2022		2021
Net gains (losses) on sales transaction	$	289	$	(1,326)	$	1,326
Net mark to mark gains (losses)		278		(237)		(273)
Net gains (losses) on trading securities	$	567	$	(1,563)	$	1,053