Investment Securities (Tables)

12 Months Ended

Dec. 31, 2019

Amortized Cost and Estimated Fair Values of Investments Securities

The amortized cost and estimated fair values of investment securities classified as available for sale and held to maturity are summarized in the following tables:


	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
			(in thousands)
Debt Securities Available for Sale
Obligations of U.S. government agencies	$	466,139	$	7,261	$	(420)	$	472,980
Obligations of states and political subdivisions	106,373		3,229		(1)		109,601
Corporate bonds	2,430		102		—		2,532
Asset backed securities	371,809		129		(6,913)		365,025
Total debt securities available for sale	$	946,751	$	10,721	$	(7,334)	$	950,138
Debt Securities Held to Maturity
Obligations of U.S. government agencies	361,785		6,072		(480)		367,377
Obligations of states and political subdivisions	13,821		327		—		14,148
Total debt securities held to maturity	$	375,606	$	6,399	$	(480)	$	381,525


	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
			(in thousands)
Debt Securities Available for Sale
Obligations of U.S. government agencies	$	647,288	$	771	$	(18,078)	$	629,981
Obligations of states and political subdivisions	128,890		294		(3,112)		126,072
Corporate bonds	4,381		97		—		4,478
Asset backed securities	355,451		73		(1,019)		354,505
Total debt securities available for sale	$	1,136,010	$	1,235	$	(22,209)	$	1,115,036
Debt Securities Held to Maturity
Obligations of U.S. government agencies	$	430,343	$	327	$	(7,745)	$	422,925
Obligations of states and political subdivisions	14,593		82		(230)		14,445
Total debt securities held to maturity	$	444,936	$	409	$	(7,975)	$	437,370

Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity

The amortized cost and estimated fair value of debt securities at December 31, 2019 by contractual maturity are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. At December 31, 2019, obligations of U.S. government and agencies with an amortized cost basis totaling $827,924,000 consist almost entirely of residential real estate mortgage-backed securities whose contractual maturity, or principal repayment, will follow the repayment of the underlying mortgages. For purposes of the following table, the entire outstanding balance of these mortgage-backed securities issued by U.S. government corporations and agencies is categorized based on final maturity date. At December 31, 2019, the Company estimates the average remaining life of these mortgage-backed securities issued by U.S. government corporations and agencies to be approximately 4.9 years. Average remaining life is defined as the time span after which the principal balance has been reduced by half.


Debt Securities	Available for Sale						Held to Maturity
(In thousands)	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year	$	607	$	611	$	1,271	$	1,280
Due after one year through five years	14,853		15,204		—		—
Due after five years through ten years	91,635		91,739		21,366		21,639
Due after ten years	839,656		842,584		352,969		358,606
Totals	$	946,751	$	950,138	$	375,606	$	381,525

Gross Unrealized Losses on Investment Securities

Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, were as follows:


	Less than 12 months						12 months or more						Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
December 31, 2019	(in thousands)
Debt Securities Available for Sale
Obligations of U.S. government agencies	$	36,709	$	(309)	$	23,852	$	(111)	$	60,561	$	(420)
Obligations of states and political subdivisions	778		(1)		—		—		778		(1)
Asset backed securities	237,463		(4,535)		99,981		(2,378)		337,444		(6,913)
Total debt securities available for sale	$	274,950	$	(4,845)	$	123,833	$	(2,489)	$	398,783	$	(7,334)
Debt Securities Held to Maturity
Obligations of U.S. government agencies	$	18,813	$	(142)	$	62,952	$	(338)	$	81,765	$	(480)
Obligations of states and political subdivisions	—		—		—		—		—		—
Total debt securities held to maturity	$	18,813	$	(142)	$	62,952	$	(338)	$	81,765	$	(480)


	Less than 12 months						12 months or more						Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
December 31, 2018	(in thousands)
Debt Securities Available for Sale
Obligations of U.S. government agencies	$	171,309	$	(3,588)	$	394,630	$	(14,490)	$	565,939	$	(18,078)
Obligations of states and political subdivisions	63,738		(1,541)		20,719		(1,571)		84,457		(3,112)
Asset backed securities	101,386		(1,019)		—		—		101,386		(1,019)
Total securities available for sale	$	336,433	$	(6,148)	$	415,349	$	(16,061)	$	751,782	$	(22,209)
Debt Securities Held to Maturity
Obligations of U.S. government agencies	$	223,810	$	(2,619)	$	158,648	$	(5,126)	$	382,458	$	(7,745)
Obligations of states and political subdivisions	5,786		(114)		4,042		(116)		9,828		(230)
Total debt securities held to maturity	$	229,596	$	(2,733)	$	162,690	$	(5,242)	$	392,286	$	(7,975)