Investment Securities

3 Months Ended

Mar. 31, 2021

Investments, Debt and Equity Securities [Abstract]

The following table presents the amortized cost and estimated fair values of investment securities for the periods presented:


	March 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available for Sale	(in thousands)


State and municipal securities	$	953,601	$	42,412	$	(1,253)	$	994,760
Corporate debt securities	348,162		11,970		(761)		359,371
Collateralized mortgage obligations	390,253		10,633		(1,005)		399,881
Residential mortgage-backed securities	257,409		1,941		(3,986)		255,364
Commercial mortgage-backed securities	668,144		12,455		(7,582)		673,017
Auction rate securities	76,350		—		(146)		76,204


Total	$	2,693,919	$	79,411	$	(14,733)	$	2,758,597

Held to Maturity

Residential mortgage-backed securities	$	467,461	$	16,303	$	(8,025)	$	475,739
Commercial mortgage-backed securities	385,952		—		(17,948)		368,004
Total	$	853,413	$	16,303	$	(25,973)	$	843,743


	December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available for Sale	(in thousands)


State and municipal securities	$	891,327	$	61,286	$	—	$	952,613
Corporate debt securities	348,391		19,445		(691)		367,145
Collateralized mortgage obligations	491,321		12,560		(115)		503,766
Residential mortgage-backed securities	373,779		4,246		(27)		377,998
Commercial mortgage-backed securities	741,172		22,384		(1,141)		762,415
Auction rate securities	101,510		—		(3,304)		98,206
Total	$	2,947,500	$	119,921	$	(5,278)	$	3,062,143



Held to Maturity

Residential mortgage-backed securities	$	278,281	$	18,576	$	—	$	296,857

During the first quarter of 2021, the Corporation transferred residential and commercial mortgage backed securities from the AFS classification to the HTM classification. The amortized cost and estimated fair value of the securities transferred were both $376.2 million.

Securities carried at $1.1 billion at March 31, 2021 and $520.5 million at December 31, 2020 were pledged as collateral to secure public and trust deposits and customer repurchase agreements.

The amortized cost and estimated fair values of debt securities as of March 31, 2021, by contractual maturity, are shown in the following table. Actual maturities may differ from contractual maturities as certain investment securities are subject to call or prepayment with or without call or prepayment penalties.


		March 31, 2021
		Available for Sale				Held to Maturity
		Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(in thousands)
Due in one year or less		$	13,107	$	13,171	$	—	$	—
Due from one year to five years		37,176		38,417		—		—
Due from five years to ten years		343,642		355,683		—		—
Due after ten years		984,188		1,023,064		—		—
		1,378,113		1,430,335		—		—
Residential mortgage-backed securities(1)		257,409		255,364		467,461		475,739
Commercial mortgage-backed securities(1)		668,144		673,017		385,952		368,004
Collateralized mortgage obligations(1)		390,253		399,881		—		—
Total		$	2,693,919	$	2,758,597	$	853,413	$	843,743

(1) Mortgage-backed securities and collateralized mortgage obligations do not have stated maturities and are dependent upon the interest rate environment and prepayments on the underlying loans.

The following table presents information related to the gross realized gains and losses on the sales of investment securities for the periods presented:


	Gross Realized Gains		Gross Realized Losses		Net Gains
Three months ended	(in thousands)
March 31, 2021	$	34,016	$	(541)	$	33,475
March 31, 2020	117		(71)		46

During the first quarter of 2021, the Corporation completed a balance sheet restructuring that included a $34.0 million gain on the sale of Visa Shares, offset by net losses on other securities of $400,000, primarily in connection with the sale of $24.6 million of ARCs. In addition, debt extinguishment costs of $32.2 million included in non-interest expense and a write-off of $841,000 in unamortized discounts was recognized in net interest income in connection with the cash tender offer for certain of its outstanding senior and subordinated notes and the prepayment of certain term FHLB advances. See Note 14, "Long-Term Debt" for further details.

The following tables present the gross unrealized losses and estimated fair values of investment securities, aggregated by category and length of time that individual securities have been in a continuous unrealized loss position for the periods presented:


	March 31, 2021
	Less than 12 months					12 months or longer					Total
	Number of Securities	Estimated Fair Value		Unrealized Losses		Number of Securities	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses

Available for Sale		(in thousands)

State and municipal securities	21	$	88,141	$	(1,253)	—	$	—	$	—	$	88,141	$	(1,253)
Corporate debt securities	7	41,956		(582)		2	15,328		(179)		57,284		(761)
Collateralized mortgage obligations	2	55,305		(1,005)		—	—		—		55,305		(1,005)
Residential mortgage-backed securities	8	173,908		(3,986)		—	—		—		173,908		(3,986)
Commercial mortgage-backed securities	10	183,175		(7,582)		—	—		—		183,175		(7,582)
Auction rate securities	—	—		—		118	76,204		(146)		76,204		(146)
Total available for sale	48	$	542,485	$	(14,408)	120	$	91,532	$	(325)	$	634,017	$	(14,733)

Held to Maturity

Residential mortgage-backed securities	12	$	205,072	$	(8,025)	—	$	—	$	—	$	205,072	$	(8,025)
Commercial mortgage-backed securities	21	368,004		(17,948)		—	—		—		368,004		(17,948)
Total	33	$	573,076	$	(25,973)	—	$	—	$	—	$	573,076	$	(25,973)


	December 31, 2020
	Less than 12 months					12 months or longer					Total
	Number of Securities	Estimated Fair Value		Unrealized Losses		Number of Securities	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
Available for Sale	(in thousands)


Corporate debt securities	9	$	44,528	$	(377)	1	$	6,871	$	(314)	$	51,399	$	(691)
Collateralized mortgage obligations	3	57,601		(115)		—	—		—		57,601		(115)
Residential mortgage-backed securities	1	20,124		(27)		—	—		—		20,124		(27)
Commercial mortgage-backed securities	9	144,383		(1,141)		—	—		—		144,383		(1,141)
Auction rate securities	—	—		—		162	98,206		(3,304)		98,206		(3,304)
Total available for sale(1)	22	$	266,636	$	(1,660)	163	$	105,077	$	(3,618)	$	371,713	$	(5,278)

(1) No HTM securities were in an unrealized loss position as of December 31, 2020.

The Corporation’s collateralized mortgage obligations and mortgage-backed securities have contractual terms that generally do not permit the issuer to settle the securities at a price less than the amortized cost of the investment. The change in fair value of these securities is attributable to changes in interest rates and not credit quality. The Corporation does not have the intent to sell and does not believe it will more likely than not be required to sell any of these securities prior to a recovery of their fair value to amortized cost. Therefore, the Corporation does not have an ACL for these investments as of March 31, 2021.

Based on management’s evaluations, no ACL was required for municipal securities, corporate debt securities or ARCs as of March 31, 2021. The Corporation does not have the intent to sell and does not believe it will more likely than not be required to sell any of these securities prior to a recovery of their fair value to amortized cost, which may be at maturity.