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Securities
 3 Months Ended
Mar. 31, 2024
Cash and Cash Equivalents [Abstract]  
Securities

Note 2 - Securities

Debt securities have been classified in the consolidated balance sheets according to management’s intent. The amortized cost, related gross unrealized gains and losses, allowance for credit losses and the fair value of available-for-sale securities are as follows (dollars in thousands):

 

 

 

March 31, 2024

 

 

 

 

 

 

Gross

 

 

Gross

 

 

 

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Estimated

 

 

 

Cost Basis

 

 

Holding Gains

 

 

Holding Losses

 

 

Fair Value

 

Securities available-for-sale:

 

 

 

 

 

 

 

 

 

 

 

 

U.S. Treasury securities

 

$

445,399

 

 

$

—

 

 

$

(13,231

)

 

$

432,168

 

Obligations of states and political subdivisions

 

 

1,592,523

 

 

 

570

 

 

 

(139,058

)

 

 

1,454,035

 

Residential mortgage-backed securities

 

 

2,685,896

 

 

 

72

 

 

 

(386,691

)

 

 

2,299,277

 

Commercial mortgage-backed securities

 

 

381,198

 

 

 

52

 

 

 

(12,344

)

 

 

368,906

 

Corporate bonds and other

 

 

112,501

 

 

 

—

 

 

 

(8,361

)

 

 

104,140

 

Total securities available-for-sale

 

$

5,217,517

 

 

$

694

 

 

$

(559,685

)

 

$

4,658,526

 

 

 

 

March 31, 2023

 

 

 

 

 

 

Gross

 

 

Gross

 

 

 

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Estimated

 

 

 

Cost Basis

 

 

Holding Gains

 

 

Holding Losses

 

 

Fair Value

 

Securities available-for-sale:

 

 

 

 

 

 

 

 

 

 

 

 

U.S. Treasury securities

 

$

508,692

 

 

$

32

 

 

$

(20,482

)

 

$

488,242

 

Obligations of states and political subdivisions

 

 

1,935,401

 

 

 

1,562

 

 

 

(163,351

)

 

 

1,773,612

 

Residential mortgage-backed securities

 

 

2,957,314

 

 

 

17

 

 

 

(374,161

)

 

 

2,583,170

 

Commercial mortgage-backed securities

 

 

364,956

 

 

 

—

 

 

 

(15,020

)

 

 

349,936

 

Corporate bonds and other

 

 

112,677

 

 

 

—

 

 

 

(9,080

)

 

 

103,597

 

Total securities available-for-sale

 

$

5,879,040

 

 

$

1,611

 

 

$

(582,094

)

 

$

5,298,557

 

 

 

 

December 31, 2023

 

 

 

 

 

 

Gross

 

 

Gross

 

 

 

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Estimated

 

 

 

Cost Basis

 

 

Holding Gains

 

 

Holding Losses

 

 

Fair Value

 

Securities available-for-sale:

 

 

 

 

 

 

 

 

 

 

 

 

U.S. Treasury securities

 

$

496,975

 

 

$

4

 

 

$

(14,745

)

 

$

482,234

 

Obligations of states and political subdivisions

 

 

1,621,405

 

 

 

934

 

 

 

(125,182

)

 

 

1,497,157

 

Residential mortgage-backed securities

 

 

2,716,968

 

 

 

7

 

 

 

(352,883

)

 

 

2,364,092

 

Commercial mortgage-backed securities

 

 

295,663

 

 

 

—

 

 

 

(11,339

)

 

 

284,324

 

Corporate bonds and other

 

 

112,670

 

 

 

—

 

 

 

(7,715

)

 

 

104,955

 

Total securities available-for-sale

 

$

5,243,681

 

 

$

945

 

 

$

(511,864

)

 

$

4,732,762

 

 

The Company did not hold any securities classified as held-to-maturity at March 31, 2024, March 31, 2023, or December 31, 2023.

The Company invests in mortgage-backed securities that have expected maturities that differ from their contractual maturities. These differences arise because borrowers may have the right to call or prepay obligations with or without a prepayment penalty. These securities include collateralized mortgage obligations (CMOs) and other asset backed securities. The expected maturities of these securities at March 31, 2024 and 2023, and December 31, 2023, were computed by using scheduled amortization of balances and historical prepayment rates.

The amortized cost and estimated fair value of available-for-sale securities at March 31, 2024, by contractual and expected maturity, are shown below (dollars in thousands):

 

 

 

Amortized

 

 

Estimated

 

 

 

Cost Basis

 

 

Fair Value

 

Due within one year

 

$

343,112

 

 

$

337,823

 

Due after one year through five years

 

 

1,374,546

 

 

 

1,288,485

 

Due after five years through ten years

 

 

2,421,721

 

 

 

2,126,343

 

Due after ten years

 

 

1,078,138

 

 

 

905,875

 

Total

 

$

5,217,517

 

 

$

4,658,526

 

 

 

The following tables disclose as of March 31, 2024 and 2023, and December 31, 2023, the Company’s investment securities that have been in a continuous unrealized-loss position for less than 12 months and for 12 or more months (dollars in thousands):

 

 

 

Less than 12 Months

 

 

12 Months or Longer

 

 

Total

 

March 31, 2024

 

Fair Value

 

 

Unrealized
Loss

 

 

Fair Value

 

 

Unrealized
Loss

 

 

Fair Value

 

 

Unrealized
Loss

 

U.S. Treasury securities

 

$

2,438

 

 

$

16

 

 

$

429,730

 

 

$

13,215

 

 

$

432,168

 

 

$

13,231

 

Obligations of states and political subdivisions

 

 

33,073

 

 

 

114

 

 

 

1,398,108

 

 

 

138,944

 

 

$

1,431,181

 

 

 

139,058

 

Residential mortgage-backed securities

 

 

22,586

 

 

 

299

 

 

 

2,261,311

 

 

 

386,392

 

 

$

2,283,897

 

 

 

386,691

 

Commercial mortgage-backed securities

 

 

64,721

 

 

 

507

 

 

 

275,924

 

 

 

11,837

 

 

$

340,645

 

 

 

12,344

 

Corporate bonds and other

 

 

—

 

 

 

—

 

 

 

104,140

 

 

 

8,361

 

 

$

104,140

 

 

 

8,361

 

Total

 

$

122,818

 

 

$

936

 

 

$

4,469,213

 

 

$

558,749

 

 

$

4,592,031

 

 

$

559,685

 

 

 

 

Less than 12 Months

 

 

12 Months or Longer

 

 

Total

 

March 31, 2023

 

Fair Value

 

 

Unrealized
Loss

 

 

Fair Value

 

 

Unrealized
Loss

 

 

Fair Value

 

 

Unrealized
Loss

 

U.S. Treasury securities

 

$

191,725

 

 

$

4,193

 

 

$

292,587

 

 

$

16,289

 

 

$

484,312

 

 

$

20,482

 

Obligations of states and political subdivisions

 

 

126,532

 

 

 

1,448

 

 

 

1,470,950

 

 

 

161,903

 

 

 

1,597,482

 

 

 

163,351

 

Residential mortgage-backed securities

 

 

91,738

 

 

 

2,937

 

 

 

2,489,524

 

 

 

371,224

 

 

 

2,581,262

 

 

 

374,161

 

Commercial mortgage-backed securities

 

 

164,301

 

 

 

3,948

 

 

 

185,635

 

 

 

11,072

 

 

 

349,936

 

 

 

15,020

 

Corporate bonds and other

 

 

42,503

 

 

 

1,167

 

 

 

61,094

 

 

 

7,913

 

 

 

103,597

 

 

 

9,080

 

Total

 

$

616,799

 

 

$

13,693

 

 

$

4,499,790

 

 

$

568,401

 

 

$

5,116,589

 

 

$

582,094

 

 

 

 

Less than 12 Months

 

 

12 Months or Longer

 

 

Total

 

December 31, 2023

 

Fair Value

 

 

Unrealized
Loss

 

 

Fair Value

 

 

Unrealized
Loss

 

 

Fair Value

 

 

Unrealized
Loss

 

U.S. Treasury securities

 

$

3,477

 

 

$

7

 

 

$

477,306

 

 

$

14,738

 

 

$

480,783

 

 

$

14,745

 

Obligations of states and political subdivisions

 

 

11,855

 

 

 

34

 

 

 

1,427,975

 

 

 

125,148

 

 

 

1,439,830

 

 

 

125,182

 

Residential mortgage-backed securities

 

 

1,631

 

 

 

1

 

 

 

2,361,089

 

 

 

352,882

 

 

 

2,362,720

 

 

 

352,883

 

Commercial mortgage-backed securities

 

 

—

 

 

 

—

 

 

 

284,324

 

 

 

11,339

 

 

 

284,324

 

 

 

11,339

 

Corporate bonds and other

 

 

—

 

 

 

—

 

 

 

104,955

 

 

 

7,715

 

 

 

104,955

 

 

 

7,715

 

Total

 

$

16,963

 

 

$

42

 

 

$

4,655,649

 

 

$

511,822

 

 

$

4,672,612

 

 

$

511,864

 

 

The number of investments in an unrealized loss position totaled 832 at March 31, 2024. We believe any unrealized losses in the U.S. treasury securities, obligations of state and political subdivisions, residential and commercial mortgage-backed and asset-backed investment securities, and corporate bonds and other at March 31, 2024 and 2023, and December 31, 2023, are due to changes in interest rates and not credit-related events. As such, no allowance for credit losses is required on these securities at March 31, 2024 and 2023, and December 31, 2023. Unrealized losses on investment securities are expected to recover over time as these securities approach maturity. Our mortgage related securities are backed by GNMA, FNMA and FHLMC or are collateralized by securities backed by these agencies. At March 31, 2024, 66.95% of our available-for-sale securities that are obligations of states and political subdivisions were issued within the State of Texas, of which 56.31% are guaranteed by the Texas Permanent School Fund.

Securities, carried at approximately $2,516,117,000 on March 31, 2024, were pledged as collateral for public or trust fund deposits, repurchase agreements, borrowings and for other purposes required or permitted by law.

During the three-months ended March 31, 2024, there were no sales of investment securities that were classified as available-for-sale. During the three-months ended March 31, 2023, sales of investment securities that were classified as available-for-sale were $145,948,000. There were no gross realized security gains or losses from sales and calls during the first quarter of 2024. Gross realized security gains from sales and calls during the first quarter of 2023 totaled $1,052,000. Gross realized security losses from sales or calls during the first quarter of 2023 totaled $1,040,000.

The specific identification method was used to determine cost in order to compute the realized gains and losses.