Securities (Tables)

3 Months Ended

Mar. 31, 2021

Investments Debt And Equity Securities [Abstract]

Schedule of Amortized Cost and Fair Value of Available-for-sale and Held-to-maturity Securities

The following table presents the fair value and amortized cost of available-for-sale and held-to-maturity debt securities:

	March 31, 2021									December 31, 2020
(unaudited, in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale debt securities
U.S. Treasury	$	29,986	$	11	$	—		$	29,997	$	39,975	$	7	$	—		$	39,982
U.S. Government sponsored entities and agencies		174,472		4,564		(2,706	)		176,330		204,109		7,715		(142	)		211,682
Residential mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		2,123,853		30,901		(13,961	)		2,140,793		1,230,106		35,979		(1,348	)		1,264,737
Commercial mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		284,440		7,962		(721	)		291,681		308,903		11,464		(269	)		320,098
Obligations of states and political subdivisions		105,778		6,056		(36	)		111,798		108,602		7,160		—			115,762
Corporate debt securities		23,953		660		—			24,613		24,963		912		—			25,875
Total available-for-sale debt securities	$	2,742,482	$	50,154	$	(17,424	)	$	2,775,212	$	1,916,658	$	63,237	$	(1,759	)	$	1,978,136
Held-to-maturity debt securities
U.S. Government sponsored entities and agencies	$	7,611	$	106	$	—		$	7,717	$	7,779	$	265	$	—		$	8,044
Residential mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		80,376		2,738		(5	)		83,109		89,151		3,251		—			92,402
Obligations of states and political subdivisions		692,616		24,501		(3,811	)		713,306		601,128		30,173		(59	)		631,242
Corporate debt securities		33,137		2,603		—			35,740		33,154		3,341		—			36,495
Total held-to-maturity debt securities	$	813,740	$	29,948	$	(3,816	)	$	839,872	$	731,212	$	37,030	$	(59	)	$	768,183
Total debt securities	$	3,556,222	$	80,102	$	(21,240	)	$	3,615,084	$	2,647,870	$	100,267	$	(1,818	)	$	2,746,319

(1) Total held-to-maturity debt securities are presented on the balance sheet net of their allowance for credit losses totaling $0.3 million at March 31, 2021 and December 31, 2020.

Schedule of Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity

The following table presents the amortized cost and fair value of available-for-sale and held-to-maturity debt securities by contractual maturity date at March 31, 2021.  Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay debt obligations with or without prepayment penalties.  Mortgage-backed securities and collateralized mortgage obligations are classified in the table below based on their contractual maturity date; however, regular principal payments and prepayments of principal are received on a monthly basis.  

(unaudited, in thousands)	Amortized Cost		Fair Value
Available-for-sale debt securities
Less than one year	$	47,465	$	47,583
1-5 years		145,739		152,800
5-10 years		358,854		366,119
Over 10 years		2,190,424		2,208,710
Total available-for-sale debt securities	$	2,742,482	$	2,775,212
Held-to-maturity debt securities
Less than one year	$	11,759	$	11,872
1-5 years		133,053		140,315
5-10 years		228,148		237,907
Over 10 years		440,780		449,778
Total held-to-maturity debt securities	$	813,740	$	839,872
Total debt securities	$	3,556,222	$	3,615,084

Schedule of Gross Realized Gains and Losses on the Sales and Calls of Securities

The following table presents the gross realized gains and losses on sales and calls of available-for-sale and held-to-maturity debt securities, as well as gains and losses on equity securities from both sales and market adjustments, for the three months ended March 31, 2021 and 2020, respectively.  All gains and losses presented in the table below are included in the net securities gains (losses) line item of the income statement.  For those equity securities relating to the key officer and director deferred compensation plan, the corresponding change in the obligation to the participant is recognized in employee benefits expense.

	For the Three Months Ended March 31,
(unaudited, in thousands)	2021			2020
Debt securities:
Gross realized gains	$	140		$	3,335
Gross realized losses		(39	)		(1,031	)
Net gains on debt securities	$	101		$	2,304
Equity securities:
Net unrealized gains (losses) recognized on securities still held	$	178		$	(805	)
Net realized losses recognized on securities sold		—			(8	)
Net gains (losses) on equity securities	$	178		$	(813	)
Net securities gains	$	279		$	1,491

Schedule of Allowance for Credit Losses on Held-to-maturity Securities

The following table provides a roll-forward of the allowance for credit losses on held-to-maturity securities for the three months ended March 31, 2021 and March 31, 2020, respectively:

	Allowance for Credit Losses By Category
	For the Three Months Ended March 31, 2021 and 2020
			Residential mortgage
			-backed
			securities and
			collateralized
			mortgage obligations		Obligations of
	U.S. Government		of government		state and			Corporate
	sponsored		sponsored entities		political			debt
(unaudited, in thousands)	entities and agencies		and agencies		subdivisions			Securities			Total
Balance at December 31, 2020	$	—	$	—	$	130		$	196		$	326
Current period provision		—		—		(12	)		(24	)		(36	)
Write-offs		—		—		—			—			—
Recoveries		—		—		—			—			—
Balance at March 31, 2021	$	—	$	—	$	118		$	172		$	290
.
Balance at December 31, 2019	$	—	$	—	$	—		$	—		$	—
Impact of adopting ASC 326		—		—		96			133			229
Current period provision		—		—		2			5			7
Write-offs		—		—		—			—			—
Recoveries		—		—		—			—			—
Balance at March 31, 2020	$	—	$	—	$	98		$	138		$	236

Schedule of Unrealized Losses on Investment Securities

The following tables provide information on unrealized losses on available-for-sale debt securities that have been in an unrealized loss position for less than twelve months and twelve months or more, for which an allowance for credit losses has not been recorded, as of March 31, 2021 and December 31, 2020, respectively:

	March 31, 2021
	Less than 12 months							12 months or more							Total
(unaudited, dollars in thousands)	Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities
U.S. Government sponsored entities and agencies	$	56,270	$	(2,706	)		6	$	—	$	—			—	$	56,270	$	(2,706	)		6
Residential mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		973,961		(13,879	)		98		3,531		(82	)		4		977,492		(13,961	)		102
Commercial mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		94,186		(721	)		9		—		—			—		94,186		(721	)		9
Obligations of state and political subdivisions		3,767		(36	)		1		—		—			—		3,767		(36	)		1
Total	$	1,128,184	$	(17,342	)		114	$	3,531	$	(82	)		4	$	1,131,715	$	(17,424	)	$	118

	December 31, 2020
	Less than 12 months							12 months or more							Total
(dollars in thousands)	Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities
U.S. Government sponsored entities and agencies	$	18,308	$	(142	)		2	$	—	$	—			—	$	18,308	$	(142	)		2
Residential mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		224,448		(1,227	)		41		4,136		(121	)		3		228,584		(1,348	)		44
Commercial mortgage-backed securities and collateralized mortgage obligations of government sponsored entities and agencies		97,266		(269	)		10		—		—			—		97,266		(269	)		10
Obligations of states and political subdivisions		—		—			—		—		—			—		—		—			—
Total	$	340,022	$	(1,638	)		53	$	4,136	$	(121	)		3	$	344,158	$	(1,759	)		56