Securities (Tables)

3 Months Ended

Mar. 31, 2021

Investments Debt And Equity Securities [Abstract]

Summary of Amortized Cost and Estimated Fair Values of Debt Securities Held for Investment

The following table summarizes the amortized cost and estimated fair values of debt securities held for investment:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
March 31, 2021	(Dollars in thousands)
Mortgage backed securities (1)	$	51	$	3	$	—		$	54
States and political subdivisions		2,405		3		(9	)		2,399
Other securities		500		—		—			500
Total	$	2,956	$	6	$	(9	)	$	2,953
December 31, 2020
Mortgage backed securities (1)	$	59	$	3	$	—		$	62
States and political subdivisions		2,405		18		(1	)		2,422
Other securities		500		—		—			500
Total	$	2,964	$	21	$	(1	)	$	2,984

Summary of Amortized Cost and Estimated Fair Values of Debt Securities Available for Sale

The following table summarizes the amortized cost and estimated fair values of debt securities available for sale:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
March 31, 2021	(Dollars in thousands)
U.S. treasuries	$	445,813	$	8,155	$	(182	)	$	453,786
U.S. federal agencies		19,166		1		(58	)		19,109
Mortgage backed securities (1)		14,877		372		—			15,249
States and political subdivisions		15,789		269		(18	)		16,040
Asset backed securities		13,341		62		—			13,403
Total	$	508,986	$	8,859	$	(258	)	$	517,587
December 31, 2020
U.S. treasuries	$	465,416	$	9,820	$	—		$	475,236
U.S. federal agencies		19,697		1		(60	)		19,638
Mortgage backed securities (1)		15,268		428		—			15,696
States and political subdivisions		28,571		377		—			28,948
Asset backed securities		13,337		—		(623	)		12,714
Total	$	542,289	$	10,626	$	(683	)	$	552,232

(1) Primarily consists of FHLMC, FNMA, GNMA and mortgage backed securities through U.S. agencies.

Maturity of Debt Securities

The maturities of debt securities held for investment and available for sale are summarized in the following table using contractual maturities. Actual maturities may differ from contractual maturities due to obligations that are called or prepaid. For purposes of the maturity table, mortgage-backed securities, which are not due at a single maturity date, have been presented at their contractual maturity.

	March 31, 2021				December 31, 2020
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(Dollars in thousands)
Held for Investment
Contractual maturity of debt securities:
Within one year	$	862	$	862	$	807	$	809
After one year but within five years		2,089		2,085		2,091		2,110
After five years but within ten years		4		5		65		64
After ten years		1		1		1		1
Total	$	2,956	$	2,953	$	2,964	$	2,984
Available for Sale
Contractual maturity of debt securities:
Within one year	$	110,317	$	111,484	$	339,752	$	341,102
After one year but within five years		359,388		366,433		162,401		171,135
After five years but within ten years		5,914		6,049		3,753		3,910
After ten years		33,367		33,621		36,383		36,085
Total debt securities	$	508,986	$	517,587	$	542,289	$	552,232

Company's Book Value of Pledged Debt Securities

The following table is a summary of the Company’s book value of securities that were pledged as collateral for public funds on deposit, repurchase agreements and for other purposes as required or permitted by law:

	March 31, 2021		December 31, 2020
	(Dollars in thousands)
Book value of pledged securities	$	459,251	$	490,833