v3.22.4
Securities (Tables)
 12 Months Ended
Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]  
Debt Securities, Held-to-maturity A summary of the amortized cost, fair value and allowance for credit losses related to securities held to maturity as of December 31, 2022 and 2021 is presented below.
Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Estimated
Fair Value		Allowance
for Credit
Losses		Net
Carrying
Amount
December 31, 2022
Residential mortgage-backed securities$526,122 $— $65,322 $460,800 $— $526,122 
States and political subdivisions2,111,619 13,048 119,033 2,005,634 (158)2,111,461 
Other1,500 — 69 1,431 — 1,500 
Total$2,639,241 $13,048 $184,424 $2,467,865 $(158)$2,639,083 
December 31, 2021
Residential mortgage-backed securities$527,264 $18,766 $— $546,030 $— $527,264 
States and political subdivisions1,220,573 41,141 101 1,261,613 (158)1,220,415 
Other1,500 — — 1,500 — 1,500 
Total$1,749,337 $59,907 $101 $1,809,143 $(158)$1,749,179 
Moody's and Standard & Poor's Bond Ratings
The following table summarizes Moody's and/or Standard & Poor's bond ratings for our portfolio of held-to-maturity securities issued by States and political subdivisions and other securities as of December 31, 2022:
States and Political Subdivisions
Not Guaranteed or Pre-RefundedGuaranteed by the Texas PSFPre-RefundedTotalOther
Securities
Aaa/AAA$273,201 $1,422,442 $121,961 $1,817,604 $— 
Aa/AA
294,015 — — 294,015 — 
Not rated— — — — 1,500 
Total$567,216 $1,422,442 $121,961 $2,111,619 $1,500 
Debt Securities, Held-to-maturity, Allowance for Credit Loss
The following table details activity in the allowance for credit losses on held-to-maturity securities.
202220212020
Beginning balance$158 $160 $— 
Impact of adopting ASC 326— — 215 
Credit loss expense (benefit)— (2)(55)
Ending balance$158 $158 $160 
Debt Securities, Available-for-sale A summary of the amortized cost, fair value and allowance for credit losses related to securities available for sale as of December 31, 2022 and 2021 is presented below.
Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Allowance
for Credit
Losses		Estimated
Fair Value
December 31, 2022
U.S. Treasury$5,450,546 $— $398,959 $— $5,051,587 
Residential mortgage-backed securities7,316,824 8,050 948,638 — 6,376,236 
States and political subdivisions7,098,635 9,108 334,388 — 6,773,355 
Other42,427 — — — 42,427 
Total$19,908,432 $17,158 $1,681,985 $— $18,243,605 
December 31, 2021
U.S. Treasury$2,165,702 $23,333 $9,602 $— $2,179,433 
Residential mortgage-backed securities4,059,692 31,662 25,089 — 4,066,265 
States and political subdivisions7,178,135 463,810 5,374 — 7,636,571 
Other42,359 — — — 42,359 
Total$13,445,888 $518,805 $40,065 $— $13,924,628 
Year End Securities with Unrealized Losses, Segregated by Length of Impairment
The table below summarizes, as of December 31, 2022, securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by type of security and length of time in a continuous unrealized loss position.
Less than 12 MonthsMore than 12 MonthsTotal
Estimated
Fair Value		Unrealized
Losses		Estimated
Fair Value		Unrealized
Losses		Estimated
Fair Value		Unrealized
Losses
U.S. Treasury
$2,012,129 $63,515 $3,039,458 $335,444 $5,051,587 $398,959 
Residential mortgage-backed securities3,265,658 345,307 2,495,906 603,331 5,761,564 948,638 
States and political subdivisions
3,923,159 136,957 681,677 197,431 4,604,836 334,388 
Total$9,200,946 $545,779 $6,217,041 $1,136,206 $15,417,987 $1,681,985 
Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity The following table summarizes the maturity distribution schedule of securities held to maturity and securities available for sale as of December 31, 2022. Mortgage-backed securities are included in maturity categories based on their stated maturity date. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations. Other securities classified as available for sale include stock in the Federal Reserve Bank and the Federal Home Loan Bank, which have no maturity date. These securities have been included in the total column only.
Within 1 Year1 - 5 Years5 - 10 YearsAfter 10 YearsTotal
Held To Maturity
Amortized Cost
Residential mortgage-backed securities$— $— $514,059 $12,063 $526,122 
States and political subdivisions123,591 24,339 8,297 1,955,392 2,111,619 
Other— 1,500 — — 1,500 
Total$123,591 $25,839 $522,356 $1,967,455 $2,639,241 
Estimated Fair Value
Residential mortgage-backed securities$— $— $450,961 $9,839 $460,800 
States and political subdivisions123,505 24,292 8,286 1,849,551 2,005,634 
Other— 1,431 — — 1,431 
Total$123,505 $25,723 $459,247 $1,859,390 $2,467,865 
Available For Sale
Amortized Cost
U. S. Treasury$249,363 $3,574,630 $1,434,504 $192,049 $5,450,546 
Residential mortgage-backed securities8 7,729 16,025 7,293,062 7,316,824 
States and political subdivisions261,477 1,464,493 937,127 4,435,538 7,098,635 
Other— — — — 42,427 
Total$510,848 $5,046,852 $2,387,656 $11,920,649 $19,908,432 
Estimated Fair Value
U. S. Treasury$240,361 $3,424,023 $1,244,812 $142,391 $5,051,587 
Residential mortgage-backed securities8 7,527 15,892 6,352,809 6,376,236 
States and political subdivisions261,888 1,470,098 918,563 4,122,806 6,773,355 
Other— — — — 42,427 
Total$502,257 $4,901,648 $2,179,267 $10,618,006 $18,243,605 
Schedule of Realized Gain (Loss) Sales of securities available for sale were as follows:
202220212020
Proceeds from sales$— $1,999,891 $1,162,352 
Gross realized gains— 69 108,989 
Gross realized losses— — — 
Tax benefit (expense) related to securities gains/losses— (14)(22,888)
Investment Income Premium amortization and discount accretion included in interest income on securities was as follows:
202220212020
Premium amortization$(110,997)$(121,994)$(126,210)
Discount accretion13,597 2,752 2,425 
Net (premium amortization) discount accretion$(97,400)$(119,242)$(123,785)
Year End Trading Account Securities, at Estimated Fair Value Year-end trading account securities, at estimated fair value, were as follows:
20222021
U.S. Treasury$25,879 $24,237 
States and political subdivisions2,166 925 
Total$28,045 $25,162 
Net Gains and Losses on Trading Account Securities
Net gains and losses on trading account securities were as follows:
202220212020
Net gain on sales transactions$3,129 $1,014 $1,102 
Net mark-to-market gains (losses)(230)(75)85 
Net gain on trading account securities$2,899 $939 $1,187