Investment Securities (Tables)

9 Months Ended

Sep. 30, 2022

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, 2022:
U.S. Government agencies	$	197,261	$	—	$	(30,091)	$	167,170
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,632,761		—		(267,505)		1,365,256
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		483,436		691		(64,602)		419,525
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		366,227		—		(66,366)		299,861
Small Business Administration loan-backed securities		58,493		—		(11,143)		47,350
	$	2,738,178	$	691	$	(439,707)	$	2,299,162
December 31, 2021:
U.S. Government agencies	$	112,913	$	—	$	(2,627)	$	110,286
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,120,104		14		(24,278)		1,095,840
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		174,178		—		(4,937)		169,241
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		350,116		304		(8,021)		342,399
Small Business Administration loan-backed securities		62,590		—		(2,292)		60,298
	$	1,819,901	$	318	$	(42,155)	$	1,778,064

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, 2022:
U.S. Treasuries	$	271,783	$	—	$	(7,358)	$	264,425
U.S. Government agencies		245,943		—		(27,320)		218,623
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		2,048,537		—		(318,470)		1,730,067
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		729,712		6		(101,906)		627,812
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,224,869		2,551		(199,644)		1,027,776
State and municipal obligations		1,256,045		23		(252,750)		1,003,318
Small Business Administration loan-backed securities		507,412		546		(43,722)		464,236
Corporate securities		35,595		10		(2,252)		33,353
	$	6,319,896	$	3,136	$	(953,422)	$	5,369,610
December 31, 2021:
U.S. Government agencies	$	98,882	$	—	$	(1,765)	$	97,117
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,851,700		5,324		(25,985)		1,831,039
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		730,949		5,957		(10,911)		725,995
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,220,233		5,438		(18,430)		1,207,241
State and municipal obligations		798,211		16,697		(2,219)		812,689
Small Business Administration loan-backed securities		502,812		2,330		(4,479)		500,663
Corporate securities		18,509		234		(9)		18,734
	$	5,221,296	$	35,980	$	(63,798)	$	5,193,478

Schedule of amortized cost and carrying value of other investment securities

	Carrying
(Dollars in thousands)	Value
September 30, 2022:
Federal Home Loan Bank stock	$	15,095
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		10,836
	$	179,755
December 31, 2021:
Federal Home Loan Bank stock	$	16,283
Federal Reserve Bank stock		129,716
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		11,006
	$	160,568

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	$	—	$	—	$	107,230	$	105,253
Due after one year through five years		101,152		92,747		487,512		466,754
Due after five years through ten years		359,629		321,679		1,149,845		999,829
Due after ten years		2,277,397		1,884,736		4,575,309		3,797,774
	$	2,738,178	$	2,299,162	$	6,319,896	$	5,369,610

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, 2022:
Securities Held to Maturity
U.S. Government agencies	$	10,903	$	98,443	$	19,188	$	68,727
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		90,161		627,193		177,344		738,063
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		34,942		265,792		29,660		104,370
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		21,199		113,354		45,167		186,507
Small Business Administration loan-backed securities		—		—		11,143		47,350
	$	157,205	$	1,104,782	$	282,502	$	1,145,017
Securities Available for Sale
U.S. Treasuries	$	7,358	$	264,425	$	—	$	—
U.S. Government agencies		12,248		159,395		15,072		59,228
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		122,435		874,957		196,035		854,926
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		35,684		368,713		66,222		257,017
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		66,849		463,425		132,795		528,853
State and municipal obligations		223,328		917,487		29,422		75,275
Small Business Administration loan-backed securities		18,118		167,715		25,604		178,604
Corporate securities		2,252		28,343		—		—
	$	488,272	$	3,244,460	$	465,150	$	1,953,903
December 31, 2021:
Securities Held to Maturity
U.S. Government agencies	$	1,745	$	86,168	$	882	$	24,118
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		18,768		868,327		5,510		184,819
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		4,937		169,240		—		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		4,902		154,963		3,119		75,450
Small Business Administration loan-backed securities		1,281		37,408		1,011		22,890
	$	31,633	$	1,316,106	$	10,522	$	307,277
Securities Available for Sale
U.S. Government agencies	$	529	$	73,353	$	1,236	$	23,763
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		17,381		1,274,934		8,604		221,435
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		10,911		432,300		—		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		13,120		846,581		5,310		98,106
State and municipal obligations		1,867		123,987		352		8,579
Small Business Administration loan-backed securities		2,720		179,168		1,759		110,309
Corporate securities		9		4,991		—		—
	$	46,537	$	2,935,314	$	17,261	$	462,192

Schedule of trading securities

	September 30,		December 31,
(Dollars in thousands)	2022		2021
U.S. Government agencies	$	12,017	$	5,154
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		11,556		6,853
Other residential mortgage issued or guaranteed by U.S. government
agencies or sponsored enterprises		5,921		12,315
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		3,116		29,667
State and municipal obligations		18,060		20,798
Other debt securities		1,270		2,902
	$	51,940	$	77,689

Summary of net (losses) gains on trading securities

	Three Months Ended September 30,				Nine Months Ended September 30,
(Dollars in thousands)	2022		2021		2022		2021
Net gains (losses) on sales transaction	$	76	$	489	$	(1,544)	$	944
Net mark to mark gains (losses)		465		(693)		(1,969)		(882)
Net gains (losses) on trading securities	$	541	$	(204)	$	(3,513)	$	62