Investment Securities (Tables)

6 Months Ended

Jun. 30, 2023

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
June 30, 2023:
U.S. Government agencies	$	197,265	$	—	$	(29,352)	$	167,913
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,514,472		—		(253,666)		1,260,806
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		460,574		—		(72,157)		388,417
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		357,815		—		(73,410)		284,405
Small Business Administration loan-backed securities		55,029		—		(12,056)		42,973
	$	2,585,155	$	—	$	(440,641)	$	2,144,514
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
June 30, 2023:
U.S. Treasuries	$	223,658	$	—	$	(3,745)	$	219,913
U.S. Government agencies		246,030		—		(27,685)		218,345
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,903,472		—		(299,102)		1,604,370
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		666,198		—		(106,422)		559,776
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,173,907		—		(211,413)		962,494
State and municipal obligations		1,135,189		3		(180,737)		954,455
Small Business Administration loan-backed securities		451,564		157		(47,162)		404,559
Corporate securities		30,558		—		(5,136)		25,422
	$	5,830,576	$	160	$	(881,402)	$	4,949,334
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
June 30, 2023:
Federal Home Loan Bank stock	$	32,085
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		10,819
	$	196,728
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	$	48,185	$	231,970	$	228,385
Due after one year through five years		51,034		45,228		301,127		283,616
Due after five years through ten years		369,168		320,965		1,263,193		1,075,431
Due after ten years		2,114,953		1,730,136		4,034,286		3,361,902
	$	2,585,155	$	2,144,514	$	5,830,576	$	4,949,334

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
June 30, 2023:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	29,352	$	167,913
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		253,666		1,260,806
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		1,549		44,665		70,608		343,752
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		73,410		284,405
Small Business Administration loan-backed securities		—		—		12,056		42,973
	$	1,549	$	44,665	$	439,092	$	2,099,849
Securities Available for Sale
U.S. Treasuries	$	—	$	—	$	3,745	$	219,913
U.S. Government agencies		560		24,440		27,126		193,905
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,252		29,385		297,850		1,574,985
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		3,230		53,808		103,192		505,968
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		7,479		71,072		203,933		891,422
State and municipal obligations		1,400		32,141		179,337		919,535
Small Business Administration loan-backed securities		240		93,998		46,922		283,088
Corporate securities		1,059		5,439		4,077		19,983
	$	15,220	$	310,283	$	866,182	$	4,608,799
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

	June 30,		December 31,
(Dollars in thousands)	2023		2022
U.S. Government agencies	$	11,049	$	11,190
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		8,265		—
Other residential mortgage issued or guaranteed by U.S. government
agencies or sponsored enterprises		3,645		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		11,705		4,589
State and municipal obligations		20,298		13,993
Other debt securities		1,618		1,491
	$	56,580	$	31,263

Summary of net gains (losses) on trading securities

	Three Months Ended June 30,				Six Months Ended June 30,
(Dollars in thousands)	2023		2022		2023		2022
Net gains (losses) on sales transaction	$	7	$	(380)	$	(40)	$	(1,620)
Net mark to mark losses		(195)		(458)		(201)		(2,434)
Net losses on trading securities	$	(188)	$	(838)	$	(241)	$	(4,054)