Investment Securities (Tables)

9 Months Ended

Sep. 30, 2021

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, 2021:
U.S. Government agencies	$	87,912	$	—	$	(2,162)	$	85,750
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,028,847		—		(19,505)		1,009,342
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		144,540		—		(4,029)		140,511
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		316,330		83		(6,586)		309,827
Small Business Administration loan-backed securities		63,856		—		(2,102)		61,754
	$	1,641,485	$	83	$	(34,384)	$	1,607,184
December 31, 2020:
U.S. Government agencies	$	25,000	$	1	$	—	$	25,001
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		632,269		1,827		(1,032)		633,064
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		75,767		405		—		76,172
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		174,506		300		(91)		174,715
Small Business Administration loan-backed securities		48,000		231		—		48,231
	$	955,542	$	2,764	$	(1,123)	$	957,183

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, 2021:
U.S. Government agencies	$	74,336	$	—	$	(1,493)	$	72,843
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,639,495		8,307		(17,354)		1,630,448
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		703,245		9,924		(5,041)		708,128
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,003,259		7,294		(11,265)		999,288
State and municipal obligations		720,417		13,218		(4,033)		729,602
Small Business Administration loan-backed securities		477,765		3,700		(4,065)		477,400
Corporate securities		13,522		323		—		13,845
	$	4,632,039	$	42,766	$	(43,251)	$	4,631,554
December 31, 2020:
U.S. Government agencies	$	29,882	$	16	$	(642)	$	29,256
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,351,506		16,657		(1,031)		1,367,132
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		739,797		16,579		(825)		755,551
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		229,219		10,939		(50)		240,108
State and municipal obligations		502,575		17,491		(27)		520,039
Small Business Administration loan-backed securities		401,496		4,978		(1,590)		404,884
Corporate securities		13,562		140		—		13,702
	$	3,268,037	$	66,800	$	(4,165)	$	3,330,672

Schedule of amortized cost and carrying value of other investment securities

	Carrying
(Dollars in thousands)	Value
September 30, 2021:
Federal Home Loan Bank stock	$	16,283
Federal Reserve Bank stock		129,716
Investment in unconsolidated subsidiaries		3,563
Other nonmarketable investment securities		11,030
	$	160,592
December 31, 2020:
Federal Home Loan Bank stock	$	15,083
Federal Reserve Bank stock		129,871
Investment in unconsolidated subsidiaries		4,941
Other nonmarketable investment securities		10,548
	$	160,443

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	$	—	$	—	$	10,948	$	10,998
Due after one year through five years		—		—		102,771		105,345
Due after five years through ten years		141,285		137,970		752,981		757,174
Due after ten years		1,500,200		1,469,214		3,765,339		3,758,037
	$	1,641,485	$	1,607,184	$	4,632,039	$	4,631,554

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				Gross
	Unrealized		Fair		Unrealized		Fair
(Dollars in thousands)	Losses		Value		Losses		Value
September 30, 2021:
Securities Held-to-Maturity
U.S. Government agencies	$	2,162	$	85,750	$	—	$	—
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		19,505		1,009,342		—		—
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		4,029		140,511		—		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		6,586		232,991		—		—
Small Business Administration loan-backed securities		2,102		61,754		—		—
	$	34,384	$	1,530,348	$	—	$	—
Securities Available for Sale
U.S. Government agencies	$	245	$	49,092	$	1,248	$	23,752
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		14,125		1,000,634		3,229		92,550
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		5,041		157,770		—		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		7,684		617,854		3,581		79,540
State and municipal obligations		3,956		238,688		77		4,025
Small Business Administration loan-backed securities		2,417		134,438		1,648		116,233
	$	33,468	$	2,198,476	$	9,783	$	316,100
December 31, 2020:
Securities Held-to-Maturity
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises	$	1,032	$	213,146	$	—	$	—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		91		27,445		—		—
	$	1,123	$	240,591	$	—	$	—
Securities Available for Sale
U.S. Government agencies	$	642	$	24,358	$	—	$	—
Residential mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		1,031		260,411		—		—
Residential collateralized mortgage-obligations issued by U.S. government
agencies or sponsored enterprises		825		140,333		—		—
Commercial mortgage-backed securities issued by U.S. government
agencies or sponsored enterprises		46		13,594		4		871
State and municipal obligations		27		8,620		—		—
Small Business Administration loan-backed securities		573		94,981		1,017		104,254
	$	3,144	$	542,297	$	1,021	$	105,125