Investment Securities (Tables)

6 Months Ended

Jun. 30, 2015

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Estimated Fair Value of Investment Securities AFS

The following table presents the amortized cost and estimated fair value of investment securities AFS as of the dates indicated. The Company’s investment in the “CRA qualified investment fund” includes shares held in a mutual fund that qualifies under the Community Reinvestment Act of 1977 for community reinvestment purposes. The Company’s holdings of equity securities in Federal Home Loan Bank of Dallas (“FHLB”) and First National Banker’s Bankshares, Inc. (“FNBB”) do not have readily determinable fair values and are carried at cost.

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(Dollars in thousands)
June 30, 2015:
Obligations of state and political subdivisions	$	496,777	$	11,768	$	(1,630	)	$	506,915
U.S. Government agency securities		257,849		4,627		(1,723	)		260,753
Corporate obligations		3,574		0		0			3,574
CRA qualified investment fund		1,028		0		(8	)		1,020
FHLB and FNBB equity securities		10,015		0		0			10,015
Total	$	769,243	$	16,395	$	(3,361	)	$	782,277
December 31, 2014:
Obligations of state and political subdivisions	$	555,335	$	18,267	$	(393	)	$	573,209
U.S. Government agency securities		245,854		6,144		(765	)		251,233
Corporate obligations		654		0		0			654
FHLB and FNBB equity securities		14,225		0		0			14,225
Total	$	816,068	$	24,411	$	(1,158	)	$	839,321
June 30, 2014:
Obligations of state and political subdivisions	$	603,533	$	15,536	$	(2,504	)	$	616,565
U.S. Government agency securities		254,878		5,613		(2,180	)		258,311
Corporate obligations		685		0		0			685
FHLB and FNBB equity securities		16,568		0		0			16,568
Total	$	875,664	$	21,149	$	(4,684	)	$	892,129

Gross Unrealized Losses and Estimated Fair Value of Investment Securities

The following table shows estimated fair value of investment securities AFS having gross unrealized losses and the amount of such unrealized losses, aggregated by investment category and length of time that individual investment securities have been in a continuous unrealized loss position, as of the dates indicated.

	Less than 12 Months				12 Months or More				Total
	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
	(Dollars in thousands)
June 30, 2015:
Obligations of state and political subdivisions	$	104,621	$	1,532	$	7,515	$	98	$	112,136	$	1,630
U.S. Government agency securities		76,252		1,534		7,181		189		83,433		1,723
CRA qualified investment fund		1,020		8		0		0		1,020		8
Total temporarily impaired securities	$	181,893	$	3,074	$	14,696	$	287	$	196,589	$	3,361
December 31, 2014:
Obligations of state and political subdivisions	$	29,174	$	75	$	34,414	$	318	$	63,588	$	393
U.S. Government agency securities		9,630		25		47,626		740		57,256		765
Total temporarily impaired securities	$	38,804	$	100	$	82,040	$	1,058	$	120,844	$	1,158
June 30, 2014:
Obligations of state and political subdivisions	$	60,769	$	386	$	79,000	$	2,118	$	139,769	$	2,504
U.S. Government agency securities		15,227		67		58,608		2,113		73,835		2,180
Total temporarily impaired securities	$	75,996	$	453	$	137,608	$	4,231	$	213,604	$	4,684

Maturity Distribution of Investment Securities AFS

The following table shows the amortized cost and estimated fair value of investment securities AFS by maturity or estimated date of repayment as of the date indicated.

	June 30, 2015
Maturity or Estimated Repayment	Amortized Cost		Estimated Fair Value
	(Dollars in thousands)
One year or less	$	36,133	$	36,619
After one year to five years		139,079		140,690
After five years to ten years		189,702		192,251
After ten years		404,329		412,717
Total	$	769,243	$	782,277

Sales Activities of Company's Investment Securities AFS are Summarized

The following table is a summary of sales activities in the Company’s investment securities AFS for the periods indicated.

	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015			2014
	(Dollars in thousands)
Sales proceeds	$	2,660	$	47,170	$	32,777		$	48,394
Gross realized gains	$	85	$	18	$	2,619		$	23
Gross realized losses		0		0		(1	)		0
Net gains on investment securities	$	85	$	18	$	2,618		$	23