Investment Securities (Tables)

6 Months Ended

Jun. 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
June 30, 2024:
U.S. Government agencies	$	147,270	$	—	$	(24,781)	$	122,489
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,370,142		—		(243,434)		1,126,708
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		428,468		—		(73,856)		354,612
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		351,181		—		(74,117)		277,064
Small Business Administration loan-backed securities		51,467		—		(11,399)		40,068
	$	2,348,528	$	—	$	(427,587)	$	1,920,941
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
June 30, 2024:
U.S. Treasuries	$	38,098	$	—	$	(153)	$	37,945
U.S. Government agencies		216,148		—		(21,025)		195,123
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,735,232		125		(286,429)		1,448,928
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		592,712		5		(102,173)		490,544
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,207,592		595		(199,225)		1,008,962
State and municipal obligations		1,124,430		1		(171,729)		952,702
Small Business Administration loan-backed securities		379,899		64		(43,221)		336,742
Corporate securities		30,509		—		(3,191)		27,318
	$	5,324,620	$	790	$	(827,146)	$	4,498,264
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
June 30, 2024:
Federal Home Loan Bank stock	$	32,336
Federal Reserve Bank stock		150,261
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		15,356
	$	201,516
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

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	$	14,057	$	143,274	$	141,624
Due after one year through five years		36,511		32,483		306,612		285,442
Due after five years through ten years		456,439		389,368		1,239,040		1,063,459
Due after ten years		1,841,213		1,485,033		3,635,694		3,007,739
	$	2,348,528	$	1,920,941	$	5,324,620	$	4,498,264

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, 2024:
Securities Held to Maturity
U.S. Government agencies	$	—	$	—	$	24,781	$	122,489
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		243,434		1,126,708
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		73,856		354,612
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		—		—		74,117		277,064
Small Business Administration loan-backed securities		—		—		11,399		40,068
	$	—	$	—	$	427,587	$	1,920,941
Securities Available for Sale
U.S. Treasuries (1)	$	—	$	10,834	$	153	$	24,815
U.S. Government agencies		—		—		21,025		195,123
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		136		8,848		286,293		1,430,209
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		—		—		102,173		489,387
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		106		16,816		199,119		920,215
State and municipal obligations		1,860		20,142		169,869		930,359
Small Business Administration loan-backed securities		2		704		43,219		317,384
Corporate securities		13		485		3,178		26,833
	$	2,117	$	57,829	$	825,029	$	4,334,325
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 June 30, 2024, had a combined gross unrealized loss total of less than $1,000.

Schedule of trading securities

	June 30,		December 31,
(Dollars in thousands)	2024		2023
U.S. Treasuries	$	20,500	$	—
U.S. Government agencies		10,220		1,537
Residential mortgage pass-through securities issued or guaranteed by U.S.
government agencies or sponsored enterprises		28,838		14,461
Other residential mortgage issued or guaranteed by U.S. government
agencies or sponsored enterprises		1,865		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		2,782		—
State and municipal obligations		26,134		14,620
Other debt securities		1,822		703
	$	92,161	$	31,321

Summary of net losses on trading securities

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(Dollars in thousands)	2024		2023		2024		2023
Net gains (losses) on sales transaction	$	170	$	7	$	224	$	(40)
Net mark to mark losses		(323)		(195)		(311)		(201)
Net losses on trading securities	$	(153)	$	(188)	$	(87)	$	(241)