Investment Securities (Tables)

9 Months Ended

Sep. 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
September 30, 2023:
U.S. Government agencies	$	197,266	$	—	$	(33,016)	$	164,250
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,474,360		—		(303,022)		1,171,338
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		451,928		—		(85,938)		365,990
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		355,664		—		(85,773)		269,891
Small Business Administration loan-backed securities		54,495		—		(13,564)		40,931
	$	2,533,713	$	—	$	(521,313)	$	2,012,400
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
September 30, 2023:
U.S. Treasuries	$	174,322	$	—	$	(2,063)	$	172,259
U.S. Government agencies		246,059		—		(29,305)		216,754
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,851,803		—		(363,097)		1,488,706
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		644,581		—		(125,154)		519,427
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,199,936		3		(250,407)		949,532
State and municipal obligations		1,132,238		1		(259,232)		873,007
Small Business Administration loan-backed securities		429,785		120		(52,435)		377,470
Corporate securities		30,546		1		(4,084)		26,463
	$	5,709,270	$	125	$	(1,085,777)	$	4,623,618
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
September 30, 2023:
Federal Home Loan Bank stock	$	18,085
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		15,243
	$	187,152
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	$	48,682	$	234,334	$	231,348
Due after one year through five years		50,994		44,922		256,202		239,370
Due after five years through ten years		407,416		341,124		1,342,414		1,104,205
Due after ten years		2,025,303		1,577,672		3,876,320		3,048,695
	$	2,533,713	$	2,012,400	$	5,709,270	$	4,623,618

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, 2023:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	33,016	$	164,250
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		303,022		1,171,338
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		85,938		365,990
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		85,773		269,891
Small Business Administration loan-backed securities		—		—		13,564		40,931
	$	—	$	—	$	521,313	$	2,012,400
Securities Available for Sale
U.S. Treasuries	$	—	$	—	$	2,063	$	172,259
U.S. Government agencies		—		—		29,305		216,754
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1		94		363,096		1,488,330
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		125,154		519,427
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		8,606		64,756		241,801		879,801
State and municipal obligations		705		9,860		258,527		860,725
Small Business Administration loan-backed securities		163		67,609		52,272		284,393
Corporate securities		—		—		4,084		25,963
	$	9,475	$	142,319	$	1,076,302	$	4,447,652
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

	September 30,		December 31,
(Dollars in thousands)	2023		2022
U.S. Government agencies	$	9,945	$	11,190
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		21,399		—
Other residential mortgage issued or guaranteed by U.S. government
agencies or sponsored enterprises		13,590		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		44,910		4,589
State and municipal obligations		16,059		13,993
Other debt securities		8,251		1,491
	$	114,154	$	31,263

Summary of net gains (losses) on trading securities

	Three Months Ended September 30,				Nine Months Ended September 30,
(Dollars in thousands)	2023		2022		2023		2022
Net (losses) gains on sales transaction	$	(76)	$	76	$	(116)	$	(1,544)
Net mark to mark gains (losses)		176		465		(25)		(1,969)
Net gains (losses) on trading securities	$	100	$	541	$	(141)	$	(3,513)