Prosperity Bancshares (PB) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
Cover [Abstract]
Entity Registrant Name	PROSPERITY BANCSHARES, INC.
Entity Central Index Key	0001068851
Trading Symbol	PB
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding (in shares)		92,939,039
Entity Current Reporting Status	Yes
Entity File Number	001-35388
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	74-2331986
Entity Address, Address Line One	Prosperity Bank Plaza
Entity Address, Address Line Two	4295 San Felipe
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77027
City Area Code	281
Local Phone Number	269-7199
Entity Shell Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $1.00 per share
Security Exchange Name	NYSE
Document Quarterly Report	true
Document Transition Report	false

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ASSETS
Cash and due from banks	$ 1,947,235	$ 1,342,996
Federal funds sold	8,986	553
Total cash and cash equivalents	1,956,221	1,343,549
Available for sale securities, at fair value	638,355	651,514
Held to maturity securities, at cost (fair value of $9,529,602 and $8,039,142, respectively)	9,449,647	7,891,306
Total securities	10,088,002	8,542,820
Loans held for sale	20,991	46,777
Loans held for investment	17,345,506	17,357,788
Total loans	19,638,886	20,246,944
Less: allowance for credit losses on loans	(307,210)	(316,068)
Loans, net	19,331,676	19,930,876
Accrued interest receivable	76,634	82,068
Goodwill	3,231,636	3,231,636
Core deposit intangibles, net	70,304	73,235
Bank premises and equipment, net	326,970	323,572
Other real estate owned	462	10,593
Bank owned life insurance (BOLI)	324,378	324,356
Federal Home Loan Bank of Dallas stock	8,901	8,901
Other assets	143,234	187,669
TOTAL ASSETS	35,558,418	34,059,275
Deposits:
Noninterest-bearing	9,820,445	9,151,233
Interest-bearing	18,942,660	18,209,259
Total deposits	28,763,105	27,360,492
Securities sold under repurchase agreements	377,106	389,583
Accrued interest payable	2,385	3,462
Allowance for credit losses on off-balance sheet credit exposures	29,947	29,947
Other liabilities	164,029	145,122
Total liabilities	29,336,572	27,928,606
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS’ EQUITY:
Preferred stock, $1 par value; 20,000,000 shares authorized; none issued or outstanding
Common stock, $1 par value; 200,000,000 shares authorized; 92,928,539 shares issued and outstanding at March 31, 2021; 92,570,789 shares issued and outstanding at December 31, 2020	92,929	92,571
Capital surplus	3,637,188	3,634,140
Retained earnings	2,490,963	2,403,189
Accumulated other comprehensive income —net unrealized gain on available for sale securities, net of tax expense of $204 and $205, respectively	766	769
Total shareholders’ equity	6,221,846	6,130,669
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	35,558,418	34,059,275
Warehouse Purchase Program [Member]
ASSETS
Loans held for investment	2,272,389	2,842,379
Total loans	$ 2,272,389	$ 2,842,379

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Held to maturity securities, fair value	$ 9,529,602	$ 8,039,142
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	92,928,539	92,570,789
Common stock, shares outstanding (in shares)	92,928,539	92,570,789
Accumulated other comprehensive income net unrealized gain on available for sale securities, tax expense	$ 204	$ 205

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
INTEREST INCOME:
Loans, including fees	$ 233,075	$ 247,243
Securities	38,677	48,282
Federal funds sold and other earning assets	351	713
Total interest income	272,103	296,238
INTEREST EXPENSE:
Deposits	17,362	35,018
Other borrowings		2,932
Securities sold under repurchase agreements	159	757
Subordinated notes		1,500
Total interest expense	17,521	40,207
NET INTEREST INCOME	254,582	256,031
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	254,582	256,031
NONINTEREST INCOME:
Nonsufficient funds (NSF) fees	6,687	9,443
Credit card, debit card and ATM card income	8,031	7,474
Service charges on deposit accounts	5,978	6,104
Trust income	2,837	2,662
Mortgage income	3,307	2,010
Brokerage income	711	650
Net loss on sale or write down of assets	(79)	(385)
Other	6,536	6,430
Total noninterest income	34,008	34,388
NONINTEREST EXPENSE:
Salaries and employee benefits	80,037	77,282
Net occupancy and equipment	7,833	8,980
Credit and debit card, data processing and software amortization	8,233	11,421
Regulatory assessments and FDIC insurance	2,670	2,078
Core deposit intangibles amortization	2,931	3,363
Depreciation	4,540	4,768
Communications	2,899	3,195
Net other real estate income	(643)	(84)
Merger related expenses		544
Other	10,576	13,194
Total noninterest expense	119,076	124,741
INCOME BEFORE INCOME TAXES	169,514	165,678
PROVISION FOR INCOME TAXES	36,205	34,830
NET INCOME	$ 133,309	$ 130,848
EARNINGS PER SHARE:
Basic	$ 1.44	$ 1.39
Diluted	$ 1.44	$ 1.39

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 133,309	$ 130,848
Securities available for sale:
Change in unrealized losses during the period	(4)	(4,183)
Total other comprehensive loss	(4)	(4,183)
Deferred tax benefit related to other comprehensive loss	1	878
Other comprehensive loss, net of tax	(3)	(3,305)
Comprehensive income	$ 133,306	$ 127,543

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	[1]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Common Stock [Member]	Common Stock [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Capital Surplus [Member]	Capital Surplus [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Retained Earnings [Member]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	[1]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
BALANCE at Dec. 31, 2019	$ 5,970,835	$ (92,860)		$ 5,877,975	$ 94,746	$ 94,746	$ 3,734,519	$ 3,734,519	$ 2,140,968	$ (92,860)		$ 2,048,108	$ 602	$ 602
BALANCE (in shares) at Dec. 31, 2019					94,746,019	94,746,019
Accounting Standards Update [Extensible List]	pb:AccountingStandardsUpdate201613AndOtherMember								pb:AccountingStandardsUpdate201613AndOtherMember
Net income	$ 130,848								$ 130,848
Other comprehensive loss	(3,305)												(3,305)
Common stock issued in connection with the issuance of restricted stock awards, net					$ (3)		3
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)					(2,750)
Common stock repurchase	(110,061)				$ (2,092)		(107,969)
Common stock repurchase (in shares)					(2,091,557)
Stock based compensation expense	3,340						3,340
Cash dividends declared	(43,223)								(43,223)
BALANCE at Mar. 31, 2020	5,855,574				$ 92,651		3,629,893		2,135,733				(2,703)
BALANCE (in shares) at Mar. 31, 2020					92,651,712
BALANCE at Dec. 31, 2020	6,130,669				$ 92,571		3,634,140		2,403,189				769
BALANCE (in shares) at Dec. 31, 2020					92,570,789
Net income	133,309								133,309
Other comprehensive loss	(3)												(3)
Common stock issued in connection with the issuance of restricted stock awards, net					$ 358		(358)
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)					357,750
Stock based compensation expense	3,406						3,406
Cash dividends declared	(45,535)								(45,535)
BALANCE at Mar. 31, 2021	$ 6,221,846				$ 92,929		$ 3,637,188		$ 2,490,963				$ 766
BALANCE (in shares) at Mar. 31, 2021					92,928,539
[1]	ASU 2016-13 became effective for the Company on January 1, 2020.

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Retained Earnings [Member]
Cash dividend declared, per share (in dollars per share)	$ 0.49	$ 0.46

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 133,309	$ 130,848
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and core deposit intangibles amortization	7,471	8,131
Net amortization of premium on investments	12,844	8,005
Net gain on sale of other real estate and repossessed assets	(887)	(130)
Net loss on sale or write down of premises and equipment	79	385
Net accretion of discount on loans	(16,341)	(28,482)
Net amortization of premium on deposits	(507)	(2,270)
Gain on sale of loans	(3,029)	(1,360)
Proceeds from sale of loans held for sale	110,602	96,119
Originations of loans held for sale	(82,777)	(79,377)
Stock based compensation expense	3,406	3,340
Decrease in accrued interest receivable and other assets	50,582	41,497
Increase in accrued interest payable and other liabilities	15,995	33,225
Net cash provided by operating activities	230,747	209,931
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities and principal paydowns of held to maturity securities	697,733	500,666
Purchase of held to maturity securities	(2,268,954)	(206,563)
Proceeds from maturities and principal paydowns of available for sale securities	313,192	4,011,040
Purchase of available for sale securities	(300,000)	(4,042,771)
Originations of WPP loans	(10,595,636)	(6,196,020)
Proceeds from pay-offs of WPP	11,165,626	6,035,020
Net decrease in loans held for investment	20,125	23,161
Purchase of bank premises and equipment	(8,020)	(6,329)
Proceeds from sale of bank premises, equipment and other real estate	10,968	2,180
Proceeds from insurance claims	1,783
Net cash (used in) provided by investing activities	(963,183)	120,384
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	669,212	(302,571)
Net increase (decrease) in interest-bearing deposits	733,908	(68,534)
Net proceeds of other short-term borrowings		35,000
Repayments of other long-term borrowings		(301)
Net decrease in securities sold under repurchase agreements	(12,477)	(32,599)
Repurchase of common stock		(110,061)
Payments of cash dividends	(45,535)	(43,223)
Net cash provided by (used in) financing activities	1,345,108	(522,289)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	612,672	(191,974)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1,343,549	574,108
CASH AND CASH EQUIVALENTS, END OF PERIOD	1,956,221	382,134
NONCASH ACTIVITIES:
Acquisition of real estate through foreclosure of collateral	281	112
SUPPLEMENTAL INFORMATION:
Interest paid	$ 18,598	$ 40,062

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. BASIS OF PRESENTATION The consolidated financial statements include the accounts of Prosperity Bancshares, Inc. ® ® The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for financial information and with the rules and regulations of the Securities and Exchange Commission. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the statements reflect all adjustments necessary for a fair presentation of the financial position, results of operations and cash flows of the Company on a consolidated basis; and all such adjustments are of a normal recurring nature. These financial statements and the notes thereto should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. Operating results for the three-month period ended March 31, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021 or any other period.

Income Per Common Share

Income Per Common Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Income Per Common Share	2. INCOME PER COMMON SHARE The following table illustrates the computation of basic and diluted earnings per share: Three Months Ended March 31, 2021 2020 Amount Per Share Amount Amount Per Share Amount (Amounts in thousands, except per share data) Net income $ 133,309 $ 130,848 Basic: Weighted average shares outstanding 92,854 $ 1.44 94,371 $ 1.39 Diluted: Weighted average shares outstanding 92,854 $ 1.44 94,371 $ 1.39 As of March 31, 2021, all stock options have been exercised and there are no options outstanding. There were no stock options exercisable during the three months ended March 31, 2021 or 2020 that would have had an anti-dilutive effect on the above computation.

New Accounting Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2021
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
New Accounting Standards	3. NEW ACCOUNTING STANDARDS Accounting Standards Updates (“ASU”) ASU 2020-04, "Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting - Accounting Standards Codification (“ASC”) Topic 848 ASU 2020-04 provides optional expedients and exceptions for applying GAAP to loan and lease agreements, derivative contracts, and other transactions affected by the anticipated transition away from LIBOR toward new interest rate benchmarks. The guidance allows for companies to: (i) account for certain contract modifications as a continuation of the existing contract without additional analysis; (ii) continue hedge accounting when certain critical terms of a hedging relationship change and assess effectiveness in ways that disregard certain potential sources of ineffectiveness; and (iii) make a one-time sale and/or transfer of certain debt securities from held-to-maturity to available-for-sale or trading. This ASU is available for adoption effective March 12, 2020 through December 31, 2022. An entity may elect to apply ASU 2020-04 for contract modifications as of January 1, 2020, or prospectively from a date within an interim period that includes or is subsequent to March 12, 2020, up to the date that the financial statements are available to be issued. Once elected for a Topic or an Industry Subtopic within ASU 2020-04, the amendments must be applied prospectively for all eligible contract modifications for that Topic or Industry Subtopic. The one-time election to sell and/or transfer debt securities classified as held-to-maturity may be made at any time after March 12, 2020. The Company anticipates this ASU will simplify any modifications it executes between the selected start date (yet to be determined) and December 31, 2022 that are directly related to the LIBOR transition by allowing prospective recognition of the continuation of the contract, rather than extinguishment of the old contract resulting in writing off unamortized fees and costs. ASU 2020-04 is not expected to have a significant impact on the Company’s financial statements.

Securities

Securities	3 Months Ended
	Mar. 31, 2021
Investments Debt And Equity Securities [Abstract]
Securities	4. SECURITIES The amortized cost and fair value of investment securities were as follows: March 31, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 600,440 $ 2,171 $ (1,192 ) $ 601,419 Mortgage-backed securities 36,945 497 (506 ) 36,936 Total $ 637,385 $ 2,668 $ (1,698 ) $ 638,355 Held to Maturity States and political subdivisions $ 144,517 $ 5,679 $ (41 ) $ 150,155 Collateralized mortgage obligations 76,073 1,584 (106 ) 77,551 Mortgage-backed securities 9,229,057 127,519 (54,680 ) 9,301,896 Total $ 9,449,647 $ 134,782 $ (54,827 ) $ 9,529,602 December 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 611,353 $ 1,601 $ (620 ) $ 612,334 Mortgage-backed securities 39,187 539 (546 ) 39,180 Total $ 650,540 $ 2,140 $ (1,166 ) $ 651,514 Held to Maturity States and political subdivisions $ 166,175 $ 8,341 $ (32 ) $ 174,484 Collateralized mortgage obligations 96,000 1,669 (219 ) 97,450 Mortgage-backed securities 7,629,131 144,710 (6,633 ) 7,767,208 Total $ 7,891,306 $ 154,720 $ (6,884 ) $ 8,039,142 The investment securities portfolio is measured for expected credit losses by segregating the portfolio into two general segments and applying the appropriate expected credit losses methodology. Investment securities classified as available for sale or held to maturity are evaluated for expected credit losses under Financial Accounting Standards Board (“FASB”): ASC 326 , “Financial Instruments – Credit Losses.” Available for sale securities . For available for sale securities in an unrealized loss position, the amount of the expected credit losses recognized in earnings depends on whether an entity intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss. If an entity intends to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the expected credit losses will be recognized in earnings equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date. If an entity does not intend to sell the security and it is not more likely than not that the entity will be required to sell the security before recovery of its amortized cost basis less any current-period loss, the expected credit losses will be separated into the amount representing the credit-related portion of the impairment loss (“credit loss”) and the noncredit portion of the impairment loss (“noncredit portion”). The amount of the total expected credit losses related to the credit loss is determined based on the difference between the present value of cash flows expected to be collected and the amortized cost basis and such difference is recognized in earnings. The amount of the total expected credit losses related to the noncredit portion is recognized in other comprehensive income, net of applicable taxes. The previous amortized cost basis less the expected credit losses recognized in earnings will become the new amortized cost basis of the investment. As of March 31, 2021, management does not have the intent to sell any of the securities classified as available for sale before a recovery of cost. In addition, management believes it is more likely than not that the Company will not be required to sell any of its investment securities before a recovery of cost. The unrealized losses are largely due to changes in market interest rates and spread relationships since the time the underlying securities were purchased. The fair value is expected to recover as the securities approach their maturity date or repricing date or if market yields for such investments decline. Management does not believe any of the securities are impaired due to reasons of credit quality. Accordingly, as of March 31, 2021 , management believes that there is no potential for credit losses on available for sale securities. Held to maturity securities . The Company’s held to maturity investments include mortgage-related bonds issued by either the Government National Mortgage Corporation (“Ginnie Mae”), Federal National Mortgage Association (“Fannie Mae”) or Federal Home Loan Mortgage Corporation (“Freddie Mac”). Ginnie Mae issued securities are explicitly guaranteed by the U.S. government, while Fannie Mae and Freddie Mac issued securities are fully guaranteed by those respective United States government-sponsored agencies, and conditionally guaranteed by the full faith and credit of the United States. The Company’s held to maturity securities also include taxable and tax-exempt municipal securities issued primarily by school districts, utility districts and municipalities located in Texas. The Company’s investment in municipal securities is exposed to credit risk. The securities are highly rated by major rating agencies and regularly reviewed by management. A significant portion are guaranteed or insured by either the Texas Permanent School Fund, Assured Guaranty or Build America Mutual. As of March 31, 2021, the Company’s municipal securities represent 1.4% of the securities portfolio. Management has the ability and intent to hold the securities classified as held to maturity until they mature, at which time the Company will receive full value for the securities. Accordingly, as of March 31, 2021, management believes that there is no potential for material credit losses on held to maturity securities. Securities with unrealized losses, segregated by length of time, that have been in a continuous loss position were as follows: March 31, 2021 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) Available for Sale Collateralized mortgage obligations $ 141,726 $ (1,181 ) $ 1,722 $ (11 ) $ 143,448 $ (1,192 ) Mortgage-backed securities 5 — 25,049 (506 ) 25,054 (506 ) Total $ 141,731 $ (1,181 ) $ 26,771 $ (517 ) $ 168,502 $ (1,698 ) Held to Maturity States and political subdivisions $ 3,177 $ (41 ) $ — $ — $ 3,177 $ (41 ) Collateralized mortgage obligations 5,583 (58 ) 3,555 (48 ) 9,138 (106 ) Mortgage-backed securities 2,763,743 (54,367 ) 27,136 (313 ) 2,790,879 (54,680 ) Total $ 2,772,503 $ (54,466 ) $ 30,691 $ (361 ) $ 2,803,194 $ (54,827 ) December 31, 2020 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) Available for Sale Collateralized mortgage obligations $ 254,318 $ (608 ) $ 2,230 $ (12 ) $ 256,548 $ (620 ) Mortgage-backed securities 74 — 26,151 (546 ) 26,225 (546 ) Total $ 254,392 $ (608 ) $ 28,381 $ (558 ) $ 282,773 $ (1,166 ) Held to Maturity States and political subdivisions $ 2,746 $ (32 ) $ — $ — $ 2,746 $ (32 ) Collateralized mortgage obligations 26,141 (219 ) — — 26,141 (219 ) Mortgage-backed securities 674,795 (6,283 ) 29,900 (350 ) 704,695 (6,633 ) Total $ 703,682 $ (6,534 ) $ 29,900 $ (350 ) $ 733,582 $ (6,884 ) At March 31, 2021 and December 31, 2020, there were 74 securities and 64 securities, respectively, in an unrealized loss position for 12 months or more. The amortized cost and fair value of investment securities at March 31, 2021, by contractual maturity, are shown below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations at any time with or without call or prepayment penalties. Held to Maturity Available for Sale Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) Due in one year or less $ 20,703 $ 20,807 $ — $ — Due after one year through five years 85,425 89,465 — — Due after five years through ten years 30,440 31,740 — — Due after ten years 7,949 8,143 — — Subtotal 144,517 150,155 — — Mortgage-backed securities and collateralized mortgage obligations 9,305,130 9,379,447 637,385 638,355 Total $ 9,449,647 $ 9,529,602 $ 637,385 $ 638,355 The Company recorded no gain or loss on the sale of securities for the three months ended March 31, 2021 and 2020. As of March 31, 2021, the Company did not own any non-agency collateralized mortgage obligations. At March 31, 2021 and December 31, 2020, the Company did not own securities of any one issuer (other than the U.S. government and its agencies) for which aggregate adjusted cost exceeded 10% of the consolidated shareholders’ equity at such respective dates. Securities with an amortized cost of $6.93 billion and $6.11 billion and a fair value of $7.02 billion and $6.23 billion at March 31, 2021 and December 31, 2020, respectively, were pledged to collateralize public deposits and for other purposes required or permitted by law.

Loans and Allowance for Credit

Loans and Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2021
Receivables [Abstract]
Loans and Allowance for Credit Losses	5. LOANS AND ALLOWANCE FOR CREDIT LOSSES The loan portfolio consists of various types of loans and is categorized by major type as follows: March 31, 2021 December 31, 2020 (Dollars in thousands) Residential mortgage loans held for sale $ 20,991 $ 46,777 Commercial and industrial 3,738,274 3,674,200 Real estate: Construction, land development and other land loans 2,031,355 1,956,960 1-4 family residential (includes home equity) 4,843,724 4,710,761 Commercial real estate (includes multi-family residential) 5,858,475 6,078,764 Farmland 401,282 410,931 Agriculture 170,501 170,421 Consumer and other 301,895 355,751 Total loans held for investment, excluding Warehouse Purchase Program 17,345,506 17,357,788 Warehouse Purchase Program 2,272,389 2,842,379 Total loans, including Warehouse Purchase Program $ 19,638,886 $ 20,246,944 Concentrations of Credit. Most of the Company’s lending activity occurs within the states of Texas and Oklahoma. Commercial real estate loans, 1-4 family residential loans and construction, land development and other land loans make up 73.3% of the Company’s total loan portfolio, excluding Warehouse Purchase Program loans, at March 31, 2021. As of March 31, 2021 and December 31, 2020, excluding Warehouse Purchase Program loans, there were no concentrations of loans related to any single industry in excess of 10% Related Party Loans. As of March 31, 2021 and December 31, 2020, loans outstanding to directors, officers and their affiliates totaled $1.6 million and $1.7 million, respectively. All transactions between the Company and such related parties are conducted in the ordinary course of business and made on the same terms and conditions as similar transactions with unaffiliated persons. An analysis of activity with respect to these related party loans is as follows: As of and for the three months ended March 31, 2021 As of and for the year ended December (Dollars in thousands) Beginning balance on January 1 $ 1,732 $ 4,152 New loans — 813 Transfers — — Repayments (87 ) (3,233 ) Ending balance $ 1,645 $ 1,732 Nonperforming Assets and Nonaccrual and Past Due Loans. The Company has several procedures in place to assist it in maintaining the overall quality of its loan portfolio. The Company has established underwriting guidelines to be followed by its officers, including requiring appraisals on loans collateralized by real estate. The Company also monitors its delinquency levels for any negative or adverse trends. Nevertheless, the Company’s loan portfolio could become subject to increasing pressures from deteriorating borrower credit due to general economic conditions. The Company generally places a loan on nonaccrual status and ceases accruing interest when the payment of principal or interest is delinquent for 90 days, or earlier in some cases, unless the loan is in the process of collection and the underlying collateral fully supports the carrying value of the loan. A loan may be returned to accrual status when all the principal and interest amounts contractually due are brought current and future principal and interest amounts contractually due are reasonably assured, which is typically evidenced by a sustained period (at least six months) of repayment performance by the borrower. With respect to potential problem loans, an evaluation of the borrower’s overall financial condition is made to determine the need, if any, for possible write downs or appropriate additions to the allowance for credit losses. An aging analysis of past due loans, segregated by category of loan, is presented below: March 31, 2021 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 5,086 $ 56 $ 5,142 $ 1,636 $ 2,024,577 $ 2,031,355 Warehouse Purchase Program loans — — — — 2,272,389 2,272,389 Agriculture and agriculture real estate (includes farmland) 369 — 369 534 570,880 571,783 1-4 family (includes home equity) (1) 6,678 32 6,710 11,425 4,846,580 4,864,715 Commercial real estate (includes multi-family residential) 22,455 225 22,680 16,671 5,819,124 5,858,475 Commercial and industrial 9,485 — 9,485 11,208 3,717,581 3,738,274 Consumer and other 872 — 872 1,551 299,472 301,895 Total $ 44,945 $ 313 $ 45,258 $ 43,025 $ 19,550,603 $ 19,638,886 December 31, 2020 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 14,820 $ 236 $ 15,056 $ 1,262 $ 1,940,642 $ 1,956,960 Warehouse Purchase Program loans — — — — 2,842,379 2,842,379 Agriculture and agriculture real estate (includes farmland) 538 — 538 1,344 579,470 581,352 1-4 family (includes home equity) (1) 7,527 36 7,563 15,999 4,733,976 4,757,538 Commercial real estate (includes multi-family residential) 17,039 1,409 18,448 10,906 6,049,410 6,078,764 Commercial and industrial 14,383 — 14,383 16,084 3,643,733 3,674,200 Consumer and other 380 18 398 1,590 353,763 355,751 Total $ 54,687 $ 1,699 $ 56,386 $ 47,185 $ 20,143,373 $ 20,246,944 (1) Includes $21.0 million and $46.8 million of residential mortgage loans held for sale at March 31, 2021 and December 31, 2020, respectively. The following table presents information regarding nonperforming assets as of the dates indicated: March 31, 2021 December 31, 2020 (Dollars in thousands) Nonaccrual loans (1) (2) $ 43,025 $ 47,185 Accruing loans 90 or more days past due 313 1,699 Total nonperforming loans 43,338 48,884 Repossessed assets 362 93 Other real estate 462 10,593 Total nonperforming assets $ 44,162 $ 59,570 Nonperforming assets to total loans and other real estate 0.22 % 0.29 % Nonperforming assets to total loans, excluding Warehouse Purchase Program loans, and other real estate 0.25 % 0.34 % (1) Includes troubled debt restructurings of $8.7 million and $11.3 million as of March 31, 2021 and December 31, 2020, respectively. (2) There were no nonperforming or troubled debt restructurings of warehouse lines of credit or Warehouse Purchase Program loans for the periods presented. The Company had $44.2 million in nonperforming assets at March 31, 2021 compared with $59.6 million at December 31, 2020. Nonperforming assets were 0.22% of total loans and other real estate at March 31, 2021 and 0.29% of total loans and other real estate at December 31, 2020. If interest on nonaccrual loans had been accrued under the original loan terms, approximately $982 thousand and $869 thousand would have been recorded as income for the three months ended March 31, 2021 and 2020, respectively. The Company had $43.0 million in nonaccrual loans at March 31, 2021 compared with $58.2 million at March 31, 2020. Acquired Loans. Acquired loans were preliminarily recorded at fair value based on a discounted cash flow valuation methodology that considers, among other things, interest rates, projected default rates, loss given default, and recovery rates. During the valuation process, the Company identified purchased credit deteriorated (“PCD”) and Non-PCD loans in the acquired loan portfolios. Loans acquired with evidence of credit quality deterioration at acquisition for which it was probable that the Company would not be able to collect all contractual amounts due were accounted for as PCD. PCD loan identification considers the following factors: payment history and past due status, debt service coverage, loan grading, collateral values and other factors that may indicate deterioration of credit quality as of the acquisition date when compared to the origination date. Non-PCD loan identification considers the following factors: account types, remaining terms, annual interest rates or coupons, current market rates, interest types, past delinquencies, timing of principal and interest payments, loan to value ratios, loss exposures and remaining balances. Accretion of purchased discounts on PCD loans will be based on future cash flows, taking into account contractual maturities. Accretion of purchased discounts on Non-PCD loans will be recognized on a level-yield basis based on contractual maturity of individual loans. PCD Loans. The recorded investment in PCD loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2021 and December 31, 2020 . March 31, 2021 December 31, 2020 (Dollars in thousands) PCD loans: Outstanding balance $ 163,191 $ 195,631 Discount (11,157 ) (14,216 ) Recorded investment $ 152,034 $ 181,415 Changes in the accretable yield for acquired PCD loans for the three months ended March 31, 2021 and 2020 were as follows: Three Months Ended March 31, 2021 2020 (Dollars in thousands) Balance at beginning of period $ 14,216 $ 35,654 Adjustments — (175 ) Accretion charge-offs (32 ) — Accretion (3,027 ) (6,019 ) Balance at March 31, $ 11,157 $ 29,460 Income recognition on PCD loans is subject to the timing and amount of future cash flows. PCD loans for which the Company is accruing interest income are not considered non-performing or impaired. The PCD discount reflected above as of March 31, 2021, represents the amount of discount available to be recognized as income. Non-PCD Loans. The recorded investment in Non-PCD loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2021 and December 31, 2020. March 31, 2021 December 31, 2020 (Dollars in thousands) Non-PCD loans: Outstanding balance $ 3,339,670 $ 3,869,205 Discount (26,285 ) (39,587 ) Recorded investment $ 3,313,385 $ 3,829,618 Changes in the discount accretion for Non-PCD loans for the three months ended March 31, 2021 and 2020 were as follows: Three Months Ended March 31, 2021 2020 (Dollars in thousands) Balance at beginning of period $ 39,587 $ 110,130 Adjustments — — Accretion charge-offs 11 (54 ) Accretion (13,313 ) (22,463 ) Balance at March 31, $ 26,285 $ 87,613 Credit Quality Indicators. As part of the on-going monitoring of the credit quality of the Company’s loan portfolio and methodology for calculating the allowance for credit losses, management assigns and tracks loan grades to be used as credit quality indicators. The following is a general description of the loan grades used: Grade 1— Credits in this category have risk potential that is virtually nonexistent. These loans may be secured by insured certificates of deposit, insured savings accounts, U.S. Government securities and highly rated municipal bonds. Grade 2— Credits in this category are of the highest quality. These borrowers represent top rated companies and individuals with unquestionable financial standing with excellent global cash flow coverage, net worth, liquidity and collateral coverage. Grade 3— Credits in this category are not immune from risk but are well protected by the collateral and paying capacity of the borrower. These loans may exhibit a minor unfavorable credit factor, but the overall credit is sufficiently strong to minimize the possibility of loss. Grade 4— Credits in this category are considered to be of acceptable credit quality with moderately greater risk than Grade 3 and receiving closer monitoring. Loans in this category have sources of repayment that remain sufficient to preclude a larger than normal probability of default and secondary sources are likewise currently of sufficient quantity, quality, and liquidity to protect the Company against loss of principal and interest. These borrowers have specific risk factors, but the overall strength of the credit is acceptable based on other mitigating credit and/or collateral factors and can repay the debt in the normal course of business. Grade 5— Credits in this category constitute an undue and unwarranted credit risk; however, the factors do not rise to a level of substandard. These credits have potential weaknesses and/or declining trends that, if not corrected, could expose the Company to risk at a future date. These loans are monitored on the Company’s internally-generated watch list and evaluated on a quarterly basis. Grade 6— Credits in this category are considered “substandard” but “non-impaired” loans in accordance with regulatory guidelines. Loans in this category have well-defined weakness that, if not corrected, could make default of principal and interest possible. Loans in this category are still accruing interest and may be dependent upon secondary sources of repayment and/or collateral liquidation. Grade 7— Credits in this category are deemed “substandard” and “impaired” pursuant to regulatory guidelines. As such, the Company has determined that it is probable that less than 100% of the contractual principal and interest will be collected. These loans are individually evaluated for a specific reserve and will typically have the accrual of interest stopped. Grade 8— Credits in this category include “doubtful” loans in accordance with regulatory guidance. Such loans are no longer accruing interest and factors indicate a loss is imminent. These loans are also deemed “impaired.” While a specific reserve may be in place while the loan and collateral are being evaluated, these loans are typically charged down to an amount the Company estimates is collectible. Grade 9— Credits in this category are deemed a “loss” in accordance with regulatory guidelines and have been charged off or charged down. The Company may continue collection efforts and may have partial recovery in the future. The following tables present loans by risk grade, by category of loan and year of origination/renewal at March 31, 2021. Term Loans Amortized Cost Basis by Origination Year 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Construction, Land Development and Other Land Loans Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 — — — — 83 175 — — 258 Grade 3 175,067 777,262 382,469 116,663 135,436 54,457 123,027 — 1,764,381 Grade 4 3,127 89,839 91,719 29,032 8,761 9,294 11,335 — 243,107 Grade 5 2,625 11,729 491 813 76 112 — — 15,846 Grade 6 — 4,442 — — — 1,192 — — 5,634 Grade 7 — 397 — 1,179 — 59 — — 1,635 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — — 154 102 238 — — — 494 Total $ 180,819 $ 883,669 $ 474,833 $ 147,789 $ 144,594 $ 65,289 $ 134,362 $ — $ 2,031,355 Agriculture and Agriculture Real Estate (includes Farmland) Grade 1 $ 463 $ 1,532 $ 377 $ 161 $ 174 $ — $ 8,785 $ 90 $ 11,582 Grade 2 — 10 — — 344 1,393 23 — 1,770 Grade 3 23,622 116,759 64,809 51,000 35,448 118,139 79,549 — 489,326 Grade 4 5,365 11,268 3,883 5,227 2,869 20,396 10,055 8 59,071 Grade 5 — 2,386 568 98 — — 2,538 — 5,590 Grade 6 — 1,281 42 59 — 836 — — 2,218 Grade 7 — 146 61 4 — 322 — — 533 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — 955 193 274 — 271 — — 1,693 Total $ 29,450 $ 134,337 $ 69,933 $ 56,823 $ 38,835 $ 141,357 $ 100,950 $ 98 $ 571,783 1-4 Family (includes Home Equity) (1) Grade 1 $ — $ 116 $ — $ — $ — $ — $ — $ — $ 116 Grade 2 77 415 306 874 433 6,741 950 — 9,796 Grade 3 396,356 1,408,886 778,786 508,016 389,576 1,099,044 115,347 1,530 4,697,541 Grade 4 4,588 11,960 21,366 25,480 26,267 46,169 2,605 — 138,435 Grade 5 — 315 318 154 501 2,438 247 — 3,973 Grade 6 — 21 65 2 2 2,405 — — 2,495 Grade 7 — 115 989 1,699 2,483 5,532 — — 10,818 Grade 8 — — — — — 38 — — 38 Grade 9 — — — — — — — — — PCD Loans — — — — — 1,503 — — 1,503 Total $ 401,021 $ 1,421,828 $ 801,830 $ 536,225 $ 419,262 $ 1,163,870 $ 119,149 $ 1,530 $ 4,864,715 Term Loans Amortized Cost Basis by Origination Year 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Commercial Real Estate (includes Multi-Family Residential) Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 596 8,826 1,444 — 6,937 1,069 — — 18,872 Grade 3 135,632 682,123 815,581 799,073 592,083 1,217,452 90,900 2,425 4,335,269 Grade 4 32,617 121,746 120,200 186,136 194,686 384,973 7,710 — 1,048,068 Grade 5 — 47,109 15,471 53,977 25,264 143,502 2,305 — 287,628 Grade 6 — 20,451 166 1,238 22,159 33,684 — — 77,698 Grade 7 — 16 — 1,201 14 9,335 1,439 — 12,005 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 35,636 25,238 6,649 664 — 10,748 — — 78,935 Total $ 204,481 $ 905,509 $ 959,511 $ 1,042,289 $ 841,143 $ 1,800,763 $ 102,354 $ 2,425 $ 5,858,475 Commercial and Industrial Grade 1 $ 543,536 $ 610,253 $ 3,274 $ 3,138 $ 678 $ 799 $ 22,920 $ 160 $ 1,184,758 Grade 2 1,398 970 8,631 510 1,085 2,153 8,504 — 23,251 Grade 3 227,659 379,975 265,630 199,222 91,252 169,696 705,395 917 2,039,746 Grade 4 7,334 54,622 58,081 47,689 9,982 17,124 140,212 975 336,019 Grade 5 33 10,735 19,074 4,655 1,408 85 7,943 81 44,014 Grade 6 451 1,792 74 168 61 3,513 8,426 — 14,485 Grade 7 163 462 288 7,710 141 1,160 20,163 — 30,087 Grade 8 — — — — — 5 — — 5 Grade 9 — — — — — — — — — PCD Loans — 41,441 808 11,170 10,131 108 2,251 — 65,909 Total $ 780,574 $ 1,100,250 $ 355,860 $ 274,262 $ 114,738 $ 194,643 $ 915,814 $ 2,133 $ 3,738,274 Consumer and Other Grade 1 $ 5,968 $ 26,100 $ 6,637 $ 2,683 $ 1,903 $ 1,150 $ 1,496 $ — $ 45,937 Grade 2 — 1,267 621 384 30,443 1,429 537 — 34,681 Grade 3 20,551 36,543 37,667 22,455 10,995 11,321 49,164 — 188,696 Grade 4 8 5,786 128 340 72 141 10,947 — 17,422 Grade 5 — 14 — 63 17 — — — 94 Grade 6 — — — — — — 9,997 — 9,997 Grade 7 — — 1,529 14 3 22 — — 1,568 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — 3,500 — — — — — — 3,500 Total $ 26,527 $ 73,210 $ 46,582 $ 25,939 $ 43,433 $ 14,063 $ 72,141 $ — $ 301,895 Term Loans Amortized Cost Basis by Origination Year 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Warehouse Purchase Program Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 — — — — — — — — — Grade 3 2,272,389 — — — — — — — 2,272,389 Grade 4 — — — — — — — — — Grade 5 — — — — — — — — — Grade 6 — — — — — — — — — Grade 7 — — — — — — — — — Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — — — — — — — — — Total $ 2,272,389 $ — $ — $ — $ — $ — $ — $ — $ 2,272,389 Total Grade 1 $ 549,967 $ 638,001 $ 10,288 $ 5,982 $ 2,755 $ 1,949 $ 33,201 $ 250 $ 1,242,393 Grade 2 2,071 11,488 11,002 1,768 39,325 12,960 10,014 — 88,628 Grade 3 3,251,276 3,401,548 2,344,942 1,696,429 1,254,790 2,670,109 1,163,382 4,872 15,787,348 Grade 4 53,039 295,221 295,377 293,904 242,637 478,097 182,864 983 1,842,122 Grade 5 2,658 72,288 35,922 59,760 27,266 146,137 13,033 81 357,145 Grade 6 451 27,987 347 1,467 22,222 41,630 18,423 — 112,527 Grade 7 163 1,136 2,867 11,807 2,641 16,430 21,602 — 56,646 Grade 8 — — — — — 43 — — 43 Grade 9 — — — — — — — — — PCD Loans 35,636 71,134 7,804 12,210 10,369 12,630 2,251 — 152,034 Total $ 3,895,261 $ 4,518,803 $ 2,708,549 $ 2,083,327 $ 1,602,005 $ 3,379,985 $ 1,444,770 $ 6,186 $ 19,638,886 (1) Includes $21.0 million of residential mortgage loans held for sale at March 31, 2021. Allowance for Credit Losses on Loans. The allowance for credit losses is adjusted through charges to earnings in the form of a provision for credit losses. Management has established an allowance for credit losses which it believes is adequate as of March 31, 2021 for estimated losses in the Company’s loan portfolio. The amount of the allowance for credit losses is affected by the following: (1) charge-offs of loans that occur when loans are deemed uncollectible and decrease the allowance, (2) recoveries on loans previously charged off that increase the allowance, (3) provisions for credit losses charged to earnings that increase the allowance, and (4) provision releases returned to earnings that decrease the allowance. Based on an evaluation of the loan portfolio and consideration of the factors listed below, management presents a quarterly review of the allowance for credit losses to the Bank’s Board of Directors, indicating any change in the allowance since the last review and any recommendations as to adjustments in the allowance. Although management believes it uses the best information available to make determinations with respect to the allowance for credit losses, future adjustments may be necessary if economic conditions or the borrower’s performance differ from the assumptions used in making the initial determinations. The Company’s allowance for credit losses on loans consists of two components: (1) a specific valuation allowance based on probable losses on specifically identified loans and (2) a general valuation allowance based on historical lifetime loan loss experience, current economic conditions, reasonable and supportable forecasted economic conditions and other qualitative risk factors both internal and external to the Company. In setting the specific valuation allowance, the Company follows a loan review program to evaluate the credit risk in the total loan portfolio and assigns risk grades to each loan. Through this loan review process, the Company maintains an internal list of impaired loans, which along with the delinquency list of loans, helps management assess the overall quality of the loan portfolio and the adequacy of the allowance for credit losses. All loans that have been identified as impaired are reviewed on a quarterly basis in order to determine whether a specific reserve is required. For certain impaired loans, the Company allocates a specific loan loss reserve primarily based on the value of the collateral securing the impaired loan in accordance with ASC Topic 326-20, “ Financial Instruments - Credit Losses. In connection with this review of the loan portfolio, the Company considers risk elements attributable to particular loan types or categories in assessing the quality of individual loans. Some of the risk elements include: • for 1-4 family residential mortgage loans, the borrower’s ability to repay the loan, including a consideration of the debt to income ratio and employment and income stability, the loan to value ratio, and the age, condition and marketability of collateral; • for commercial real estate loans and multifamily residential loans, the debt service coverage ratio (income from the property in excess of operating expenses compared to loan payment requirements), operating results of the owner in the case of owner-occupied properties, the loan to value ratio, the age and condition of the collateral and the volatility of income, property value and future operating results typical of properties of that type; • for construction, land development and other land loans, the perceived feasibility of the project including the ability to sell developed lots or improvements constructed for resale or the ability to lease property constructed for lease, the quality and nature of contracts for presale or prelease, if any, experience and ability of the developer and loan to value ratio; • for commercial and industrial loans, the operating results of the commercial, industrial or professional enterprise, the borrower’s business, professional and financial ability and expertise, the specific risks and volatility of income and operating results typical for businesses in that category and the value, nature and marketability of collateral; • for the Warehouse Purchase Program, the capitalization and liquidity of the mortgage banking client, the operating experience, the client’s satisfactory underwriting of purchased loans and the consistent timeliness by client of loan resale to investors; • for agriculture real estate loans, the experience and financial capability of the borrower, projected debt service coverage of the operations of the borrower and loan to value ratio; and • for non-real estate agriculture loans, the operating results, experience and financial capability of the borrower, historical and expected market conditions and the value, nature and marketability of collateral. In addition, for each category, the Company considers secondary sources of income and the financial strength and credit history of the borrower and any guarantors. In determining the amount of the general valuation allowance, management considers factors such as historical lifetime loan loss experience, concentration risk of specific loan types, the volume, growth and composition of the Company’s loan portfolio, current economic conditions and reasonable and supportable forecasted economic conditions that may affect the borrower’s ability to pay and the value of collateral, the evaluation of the Company’s loan portfolio through its internal loan review process, general economic conditions and other qualitative risk factors both internal and external to the Company and other relevant factors in accordance with ASC Topic 326, “ Financial Instruments – Credit Losses.” The following table details activity in the allowance for credit losses on loans by category of loan for the three months ended March 31, 2021 and 2020. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Allowance for credit losses: Three Months Ended Balance December 31, 2020 $ 44,892 $ 7,824 $ 44,555 $ 87,857 $ 116,795 $ 14,145 $ 316,068 Provision for credit losses 5,221 312 3,194 4,572 (9,816 ) (3,483 ) — Charge-offs — (38 ) (54 ) (6,589 ) (1,754 ) (935 ) (9,370 ) Recoveries 5 5 7 — 170 325 512 Net charge-offs 5 (33 ) (47 ) (6,589 ) (1,584 ) (610 ) (8,858 ) Balance March 31, 2021 $ 50,118 $ 8,103 $ 47,702 $ 85,840 $ 105,395 $ 10,052 $ 307,210 Allowance for credit losses: Three Months Ended Balance December 31, 2019 $ 14,654 $ 2,971 $ 15,277 $ 12,332 $ 40,445 $ 1,790 $ 87,469 Impact of adoption ASU 2016-13 14,075 2,797 8,267 48,990 139,624 26,785 240,538 Provision for credit losses — — — — — — — Charge-offs — (31 ) (29 ) — (611 ) (1,316 ) (1,987 ) Recoveries 12 32 24 81 639 398 1,186 Net charge-offs 12 1 (5 ) 81 28 (918 ) (801 ) Balance March 31, 2020 $ 28,741 $ 5,769 $ 23,539 $ 61,403 $ 180,097 $ 27,657 $ 327,206 The allowance for credit losses on loans as of March 31, 2021 totaled $307.2 million or 1.56% of total loans, including acquired loans with discounts, a decrease of $8.9 million or 2.8% compared to the allowance for credit losses on loans totaling $316.1 million or 1.56% of total loans, including acquired loans with discounts, as of December 31, 2020. Net charge-offs were $8.9 million for the three months ended March 31, 2021. Net charge-offs for the first quarter of 2021 included $7.1 million related to resolved PCD loans, which had specific reserves that were allocated to the charge-offs. Additionally, $4.2 million of specific reserves on resolved PCD loans was released to the general reserve without taking any charge-off. As of March 31, 2021, the Company also had loans totaling $1.14 billion pursuant to the Paycheck Protection Program (“PPP”), which are fully guaranteed by the Small Business Administration and do not carry an allowance. Allowance for Credit Losses on Off-Balance Sheet Credit Exposures. The allowance for credit losses on off-balance sheet credit exposures estimates expected credit losses over the contractual period in which there is exposure to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The allowance is adjusted as a provision for credit loss expense. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on the commitments expected to fund. The estimate of commitments expected to fund is affected by historical analysis of utilization rates. The expected credit loss rates applied to the commitments expected to fund are affected by the general valuation allowance utilized for outstanding balances with the same underlying assumptions and drivers. As of March 31, 2021 and December 31, 2020, the Company had $29.9 million in allowance for credit losses on off-balance sheet credit exposures. The allowance for credit losses on off-balance sheet credit exposures is a separate line item on the Company’s consolidated balance sheet. As of March 31, 2021, the Company had $1.64 billion in commitments expected to fund. Troubled Debt Restructurings. The restructuring of a loan is considered a “troubled debt restructuring” if both (1) the borrower is experiencing financial difficulties and (2) the creditor has granted a concession. Concessions may include interest rate reductions or below market interest rates, principal forgiveness, restructuring amortization schedules and other actions intended to minimize potential losses. Under ASC Topic 310-40 “ the Company evaluates all loan modifications to identify whether the restructuring constitutes a troubled debt restructuring. As of March 31, 2021 and 2020, the Company had $8.7 million and $13.0 million, respectively, in outstanding troubled debt restructurings As of March 31, 2021, there have been no defaults on any loans that were modified as troubled debt restructurings during the preceding twelve months. Default is determined at 90 or more days past due. The modifications generally relate to extending the amortization periods of the loans, which includes loans modified during bankruptcy. For the three months ended March 31, 2021 and 2020, the Company did not add any loans as new troubled debt restructurings. Under the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) and the Consolidated Appropriations Act of 2021 (“CAA”) , banks may deem that loan modifications do not result in troubled debt restructurings if they are (1) related to the novel strain of coronavirus disease first reported in December 2019 (“COVID-19”) ; (2) executed on a loan that was not more than 30 days past due as of December 31, 2019; and (3) executed between March 1, 2020, and the earlier of (A) 60 days after the date of termination of the COVID-19 national emergency declaration by the President of the United States or (B) January 1, 2022. Additionally, other short-term modifications made on a good faith basis in response to COVID-19 to borrowers who were current prior to any relief are not troubled debt restructurings under ASC Subtopic 310-40 and federal banking agencies’ interagency guidance. These modifications include modifications such as principal and interest payment deferrals, temporary interest only payment terms, fee waivers, extensions of repayment terms, or delays in payment that are insignificant. Borrowers considered current are those that are less than 30 days past due on their contractual payments at the time a modification program is implemented. The Company's troubled debt restructurings do not include loan modifications related to COVID-19. Beginning in mid-March of 2020, the Company began offering deferral and modification of principal and/or interest payments to selected borrowers on a case-by-case basis. As of March 31, 2021, the Company had approximately $ 316.7 million in outstanding loans subject to deferral and modification agreements.

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value	6. FAIR VALUE The Company uses fair value measurements to record fair value adjustments to certain assets and to determine fair value disclosures. Fair values represent the estimated price that would be received from selling an asset or paid to transfer a liability, otherwise known as an “exit price.” Securities available for sale are recorded at fair value on a recurring basis. Additionally, from time to time, the Company may be required to record at fair value other assets on a nonrecurring basis. These nonrecurring fair value adjustments typically involve application of lower-of-cost-or-market accounting or write downs of individual assets. ASC Topic 820, “Fair Value Measurements and Disclosures” Fair Value Hierarchy The Company groups financial assets and financial liabilities measured at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. These levels are: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Other significant observable inputs (including quoted prices in active markets for similar assets or liabilities) or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, the Company utilizes valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. The fair value disclosures below represent the Company’s estimates based on relevant market information and information about the financial instruments. Fair value estimates are based on judgments regarding current economic conditions, risk characteristics of the various instruments and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in the above methodologies and assumptions could significantly affect the estimates. The following tables present fair values for assets and liabilities measured at fair value on a recurring basis: As of March 31, 2021 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: Collateralized mortgage obligations $ — $ 601,419 $ — $ 601,419 Mortgage-backed securities — 36,936 — 36,936 Total $ — $ 638,355 $ — $ 638,355 Derivative financial instruments: Loan customer counterparty $ — $ 8,881 $ — $ 8,881 Financial institution counterparty — — — — Liabilities: Derivative financial instruments: Loan customer counterparty $ — $ — $ — $ — Financial institution counterparty — 8,881 — 8,881 As of December 31, 2020 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: Collateralized mortgage obligations $ — $ 612,334 $ — $ 612,334 Mortgage-backed securities — 39,180 — 39,180 Total available for sale securities $ — $ 651,514 $ — $ 651,514 Derivative financial instruments: Loan customer counterparty — 11,912 — 11,912 Financial institution counterparty — — — — Liabilities: Derivative financial instruments: Loan customer counterparty — — — — Financial institution counterparty — 11,912 — 11,912 Certain assets and liabilities are measured at fair value on a nonrecurring basis; that is, the instruments are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). These instruments include other real estate owned, repossessed assets, held to maturity debt securities, loans held for sale and impaired loans, which are included as loans held for investment. For the three months ended March 31, 2021, the Company had additions to other real estate owned of $281 thousand, of which $150 thousand were outstanding as of March 31, 2021. For the three months ended March 31, 2021, the Company had additions to impaired loans of $4.4 million, of which $4.4 million were outstanding as of March 31, 2021. The remaining financial assets and liabilities measured at fair value on a non-recurring basis that were recorded in 2021 and remained outstanding at March 31, 2021 were not significant. The following tables present carrying and fair value information of financial instruments as of the dates indicated: As of March 31, 2021 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 1,947,235 $ 1,947,235 $ — $ — $ 1,947,235 Federal funds sold 8,986 8,986 — — 8,986 Held to maturity securities 9,449,647 — 9,529,602 — 9,529,602 Loans held for sale 20,991 — 20,991 — 20,991 Loans held for investment, net of allowance 17,038,296 — — 17,137,592 17,137,592 Loans held for investment - Warehouse Purchase Program 2,272,389 — 2,272,389 — 2,272,389 Other real estate owned 462 — 462 — 462 Liabilities Deposits: Noninterest-bearing $ 9,820,445 $ — $ 9,820,445 $ — $ 9,820,445 Interest-bearing 18,942,660 — 18,954,529 — 18,954,529 Securities sold under repurchase agreements 377,106 — 377,115 — 377,115 As of December 31, 2020 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 1,342,996 $ 1,342,996 $ — $ — $ 1,342,996 Federal funds sold 553 553 — — 553 Held to maturity securities 7,891,306 — 8,039,142 — 8,039,142 Loans held for sale 46,777 — 46,777 — 46,777 Loans held for investment, net of allowance 17,041,720 — — 17,118,745 17,118,745 Loans held for investment - Warehouse Purchase Program 2,842,379 — 2,842,379 — 2,842,379 Other real estate owned 10,593 — 10,593 — 10,593 Liabilities Deposits: Noninterest-bearing $ 9,151,233 $ — $ 9,151,233 $ — $ 9,151,233 Interest-bearing 18,209,259 — 18,227,623 — 18,227,623 Securities sold under repurchase agreements 389,583 — 389,595 — 389,595 The following is a description of the fair value estimates, methods and assumptions that are used by the Company in estimating the fair values of financial instruments. Loans held for sale — Loans held for sale are carried at the lower of cost or estimated fair value. Fair value for consumer mortgages held for sale is based on commitments on hand from investors or prevailing market prices. As such, the Company classifies loans held for sale subjected to nonrecurring fair value adjustments as Level 2. Loans held for investment — The Company does not record loans at fair value on a recurring basis. As such, valuation techniques discussed herein for loans are primarily for estimating fair value disclosures. The Company refined the calculation to estimate fair value for loans held for investment to be in accordance with ASU 2016-01. The refined discounted cash flow calculation to determine fair value considers internal and market-based information such as prepayment risk, cost of funds and liquidity. From time to time, the Company records nonrecurring fair value adjustments to impaired loans to reflect (1) partial write downs that are based on the observable market price or current appraised value of the collateral, or (2) the full charge-off of the loan carrying value. Where appraisals are not available, estimated cash flows are discounted using a rate commensurate with the credit risk associated with those cash flows. Assumptions regarding credit risk, cash flows and discount rates are judgmentally determined using available market information and specific borrower information. The Company classifies the estimated fair value of loans held for investment as Level 3. Other real estate owned — Other real estate owned is primarily foreclosed properties securing residential loans and commercial real estate. Foreclosed assets are adjusted to fair value less estimated costs to sell upon transfer of the loans to other real estate owned. Subsequently, these assets are carried at the lower of carrying value or fair value less estimated costs to sell. Other real estate carried at fair value based on an observable market price or a current appraised value is classified by the Company as Level 2. When management determines that the fair value of other real estate requires additional adjustments, either as a result of a non-current appraisal or when there is no observable market price, the Company classifies the other real estate as Level 3. The fair value estimates presented herein are based on pertinent information available to management at March 31, 2021. Although management is not aware of any factors that would significantly affect the estimated fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since those dates and, therefore, current estimates of fair value may differ significantly from the amounts presented herein.

Goodwill and Core Deposit Intan

Goodwill and Core Deposit Intangibles	3 Months Ended
	Mar. 31, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Core Deposit Intangibles	7. GOODWILL AND CORE DEPOSIT INTANGIBLES Changes in the carrying amount of the Company’s goodwill and core deposit intangibles for the three months ended March 31, 2021 and the year ended December 31, 2020 were as follows: Goodwill Core Deposit Intangibles (Dollars in thousands) Balance as of December 31, 2019 $ 3,223,671 $ 86,404 Less: Amortization — (13,169 ) Add: Measurement period adjustment of LegacyTexas Merger ( 1) 7,965 — Balance as of December 31, 2020 3,231,636 73,235 Less: Amortization — (2,931 ) Balance as of March 31, 2021 $ 3,231,636 $ 70,304 (1) LegacyTexas Financial Group, Inc. (“LegacyTexas”) merged into Bancshares on November 1, 2019. Goodwill is recorded as of the acquisition date of each entity. The Company may record subsequent adjustments to goodwill for amounts undeterminable at acquisition date, such as deferred taxes and real estate valuations, and therefore the goodwill amounts may change accordingly. The Company initially records the total premium paid on acquisitions as goodwill. After finalizing the valuation, core deposit intangibles are identified and reclassified from goodwill to core deposit intangibles on the balance sheet. This reclassification has no effect on total assets, liabilities, shareholders’ equity, net income or cash flows. Management performs an evaluation annually, and more frequently if a triggering event occurs, of whether any impairment of the goodwill and core deposit intangibles has occurred. If any such impairment is determined, a write-down is recorded. As of March 31, 2021, there was no impairment recorded on goodwill and core deposit intangibles. The measurement period for the Company to determine the fair value of acquired identifiable assets and assumed liabilities will be at the end of the earlier of (1) twelve months from the date of acquisition or (2) as soon as the Company receives the information it was seeking about facts and circumstances that existed as of the date of acquisition. Core deposit intangibles are being amortized on a non-pro rata basis over their estimated lives, which the Company believes is between 10 and 15 years. Amortization expense related to intangible assets totaled $2.9 million and $3.4 million for the three months ended March 31, 2021 and 2020, respectively. The estimated aggregate future amortization expense for core deposit intangibles remaining as of March 31, 2021 is as follows (dollars in thousands): Remaining 2021 $ 8,621 2022 10,336 2023 9,360 2024 8,699 2025 8,173 Thereafter 25,115 Total $ 70,304

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	8. STOCK–BASED COMPENSATION At March 31, 2021, the Company had two stock-based employee compensation plans with awards outstanding. On March 3, 2020, Bancshares’ Board of Directors established the Prosperity Bancshares, Inc. 2020 Stock Incentive Plan (the “2020 Plan”), which was approved by the Company’s shareholders on April 21, 2020. The 2020 Plan authorizes the issuance of up to 2,500,000 shares of common stock upon the exercise of options or pursuant to the grant or exercise, as the case may be, of other awards granted under the 2020 Plan, including incentive stock options, nonqualified stock options, stock appreciation rights, shares of restricted stock and restricted stock units. As of March 31, 2021, 4,576 shares of common stock had been issued pursuant to vested awards and 391,155 shares of unvested restricted stock have been granted under the 2020 Plan. During 2012, Bancshares’ Board of Directors established the Prosperity Bancshares, Inc. 2012 Stock Incentive Plan (the “2012 Plan”), which was approved by Bancshares’ shareholders and authorized the issuance of up to 1,250,000 shares of common stock upon the exercise of options granted under the 2012 Plan or pursuant to the grant or exercise, as the case may be, of other awards granted under the 2012 Plan, including restricted stock, stock appreciation rights, phantom stock awards and performance awards. As of March 31, 2021, 696,388 shares of common stock had been issued pursuant to vested awards and 149,987 shares of unvested restricted stock had been granted under the 2012 Plan prior to the adoption of the 2020 Plan by the Company’s shareholders. The Company does not plan to make any further awards pursuant to the 2012 Plan. As of March 31, 2021, the Company had no stock options outstanding. Stock-based compensation expense related to restricted stock was $3.4 million and $3.3 million during the three months ended March 31, 2021 and 2020, respectively. As of March 31, 2021, there was $29.3 million of total unrecognized compensation expense related to stock-based compensation arrangements. That cost is expected to be recognized over a weighted average period of 1.97 years.

Contractual Obligations and Off

Contractual Obligations and Off-Balance Sheet Items	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Contractual Obligations and Off-Balance Sheet Items	9. CONTRACTUAL OBLIGATIONS AND OFF-BALANCE SHEET ITEMS The Company’s leases and off-balance sheet items as of March 31, 2021 are summarized below. Leases The Company’s leases relate primarily to operating leases for office space and banking centers. The Company determines if an arrangement is a lease or contains a lease at inception. The Company’s leases have remaining lease terms of 1 to 18 years, which may include the option to extend the lease when it is reasonably certain for the Company to exercise that option. Operating lease right-of-use (ROU) assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. The Company uses its incremental collateralized borrowing rate to determine the present value of lease payments. Short-term leases and leases with variable lease costs are immaterial and the Company has one sublease arrangement. Sublease income for the three months ended March 31, 2021 was $450 thousand and the Company had no sublease income for the three months ended March 31, 2020. As of March 31, 2021, operating lease ROU assets and lease liabilities were approximately $54.7 million. ROU assets and lease liabilities were classified as other assets and other liabilities, respectively. As of March 31, 2021, the weighted average remaining lease terms of the Company’s operating leases were 6.9 years. The weighted average discount rate used to determine the lease liabilities as of March 31, 2021 for the Company’s operating leases was 2.26%. Cash paid for the Company’s operating leases for the three months ended March 31, 2021 and 2020 was $3.5 million and $3.6 million, respectively. The Company obtained $258 thousand in ROU assets in exchange for lease liabilities for one operating lease during the three months ended March 31, 2021. The Company’s future undiscounted cash payments associated with its operating leases as of March 31, 2021 are summarized below (dollars in thousands). Remaining 2021 $ 8,305 2022 10,608 2023 9,860 2024 8,938 2025 8,546 2026 7,853 Thereafter 12,716 Total undiscounted lease payments $ 66,826 Off-Balance Sheet Items In the normal course of business, the Company enters into various transactions that, in accordance with GAAP, are not included in its consolidated balance sheets. The Company enters into these transactions to meet the financing needs of its customers. These transactions include commitments to extend credit and standby letters of credit, which involve, to varying degrees, elements of credit risk and interest rate risk in excess of the amounts recognized in the consolidated balance sheets. The Company’s commitments associated with outstanding standby letters of credit, unused capacity on Warehouse Purchase Program loans and commitments to extend credit expiring by period as of March 31, 2021 are summarized below. Since commitments associated with letters of credit, unused capacity of Warehouse Purchase Program loans and commitments to extend credit may expire unused, the amounts shown do not necessarily reflect the actual future cash funding requirements. 1 year or less More than 1 year but less than 3 years 3 years or more but less than 5 years 5 years or more Total (Dollars in thousands) Standby letters of credit $ 96,944 $ 6,133 $ 803 $ — $ 103,880 Unused capacity on Warehouse Purchase Program loans 1,500,611 — — — 1,500,611 Commitments to extend credit 1,713,071 779,833 369,880 1,127,890 3,990,674 Total $ 3,310,626 $ 785,966 $ 370,683 $ 1,127,890 $ 5,595,165 The Company funds an allowance for credit losses on off-balance sheet lending-related commitments and guarantees on credit card debt through a charge to provision for credit losses on the Company’s consolidated statement of income. At March 31, 2021 and December 31, 2020, this allowance for credit losses on off-balance sheet lending-related commitments and guarantees on credit card debt, included in “Allowance for credit losses on off-balance sheet credit exposures” on the Company’s consolidated balance sheet, totaled $29.9 million.

Other Comprehensive Income

Other Comprehensive Income	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Other Comprehensive Income	10. OTHER COMPREHENSIVE INCOME The tax effects allocated to each component of other comprehensive income were as follows: Three Months Ended March 31, 2021 2020 Before Tax Amount Tax Effect Net of Tax Amount Before Tax Amount Tax Effect Net of Tax Amount (Dollars in thousands) Other comprehensive loss: Securities available for sale: Change in unrealized loss during period $ (4 ) $ 1 $ (3 ) $ (4,183 ) $ 878 $ (3,305 ) Total securities available for sale (4 ) 1 (3 ) (4,183 ) 878 (3,305 ) Total other comprehensive loss $ (4 ) $ 1 $ (3 ) $ (4,183 ) $ 878 $ (3,305 ) Activity in accumulated other comprehensive income associated with securities available for sale, net of tax, was as follows: Securities Available for Sale Accumulated Other Comprehensive Income (Loss) (Dollars in thousands) Balance at December 31, 2020 $ 769 $ 769 Other comprehensive loss (3 ) (3 ) Balance at March 31, 2021 $ 766 $ 766 Balance at December 31, 2019 $ 602 $ 602 Other comprehensive loss (3,305 ) (3,305 ) Balance at March 31, 2020 $ (2,703 ) $ (2,703 )

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2021
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	11. DERIVATIVE FINANCIAL INSTRUMENTS The following table provides the outstanding notional balances and fair values of outstanding derivative positions at March 31, 2021 and December 31, 2020. March 31, 2021 December 31, 2020 Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value (Dollars in thousands) Commercial loan interest rate swaps and caps: Loan customer counterparty $ 249,433 $ 8,881 $ — $ 224,684 $ 11,912 $ — Financial institution counterparty 249,433 — 8,881 224,684 — 11,912 These financial instruments are not designated as hedging instruments and are used for asset and liability management and commercial customers’ financing needs. All derivatives are carried at fair value in either other assets or other liabilities. Interest rate lock commitments (“IRLCs”) — In the normal course of business, the Company enters into interest rate lock commitments with consumers to originate mortgage loans at a specified interest rate. These commitments, which contain fixed expiration dates, offer the borrower an interest rate guarantee provided the loan meets underwriting guidelines and closes within the timeframe established by the Company. Forward mortgage-backed securities trades — The Company manages the changes in fair value associated with changes in interest rates related to IRLCs by using forward sold commitments known as forward mortgage-backed securities trades. These instruments are typically entered into at the time the interest rate lock commitment is made. Interest rate swaps and caps — These derivative positions relate to transactions in which the Company enters into an interest rate swap or cap with a customer, while at the same time entering into an offsetting interest rate swap or cap with another financial institution. An interest rate swap transaction allows the Company’s customer to effectively convert a variable rate loan to a fixed rate. In connection with each swap, the Company agrees to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on a similar notional amount at a fixed interest rate. At the same time, the Company agrees to pay another financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. In connection with each interest rate cap, the Company sells a cap to the customer and agrees to pay interest if the underlying index exceeds the strike price defined in the cap agreement. Simultaneously the Company purchases a cap with matching terms from another financial institution that agrees to pay the Company if the underlying index exceeds the strike price. The commercial loan customer counterparty weighted average received and paid interest rates for interest rate swaps outstanding at March 31, 2021 and December 31, 2020 are presented in the following table. Weighted-Average Interest Rate March 31, 2021 December 31, 2020 Received Paid Received Paid Loan customer counterparty 2.62 % 0.68 % 2.83 % 0.79 % The Company’s credit exposure on interest rate swaps is limited to the net favorable value of all swaps by each counterparty, which was approximately $8.9 million at March 31, 2021 and $11.9 million at December 31, 2020. This credit exposure is partly mitigated as transactions with customers are secured by the collateral, if any, securing the underlying transaction being hedged. The Company’s credit exposure, net of collateral pledged, relating to interest rate swaps with upstream financial institution counter-parties was zero at March 31, 2021. A credit support annex is in place and allows the Company to call collateral from upstream financial institution counter-parties. Collateral levels are monitored and adjusted on a regular basis for changes in interest rate swap values. The Company’s cash collateral pledged for interest rate swaps was $10.3 million at March 31, 2021 and $13.8 The initial and subsequent changes in the fair value of IRLCs and the forward sales of mortgage-back ed securities are recorded in net gain on sale of mortgage loans. These gains and losses were not attributable to instrument-specific credit risk. For interest rate swaps and caps, because the Company acts as an intermediary for its customer, changes in the fair value of the underlying derivative contracts substantially offset each other and do not have a material impact on its results of operations. Income (loss) for the three months ended March 31, 2021 and 20 20 was as follows: Three Months Ended March 31, Derivatives not designated as hedging instruments 2021 2020 (Dollars in thousands) Interest rate lock commitments $ — $ 1,112 Forward mortgage-backed securities trades — (1,937 )

New Accounting Standards (Polic

New Accounting Standards (Policies)	3 Months Ended
	Mar. 31, 2021
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Accounting Standards Updates (''ASU'')	Accounting Standards Updates (“ASU”) ASU 2020-04, "Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting - Accounting Standards Codification (“ASC”) Topic 848 ASU 2020-04 provides optional expedients and exceptions for applying GAAP to loan and lease agreements, derivative contracts, and other transactions affected by the anticipated transition away from LIBOR toward new interest rate benchmarks. The guidance allows for companies to: (i) account for certain contract modifications as a continuation of the existing contract without additional analysis; (ii) continue hedge accounting when certain critical terms of a hedging relationship change and assess effectiveness in ways that disregard certain potential sources of ineffectiveness; and (iii) make a one-time sale and/or transfer of certain debt securities from held-to-maturity to available-for-sale or trading. This ASU is available for adoption effective March 12, 2020 through December 31, 2022. An entity may elect to apply ASU 2020-04 for contract modifications as of January 1, 2020, or prospectively from a date within an interim period that includes or is subsequent to March 12, 2020, up to the date that the financial statements are available to be issued. Once elected for a Topic or an Industry Subtopic within ASU 2020-04, the amendments must be applied prospectively for all eligible contract modifications for that Topic or Industry Subtopic. The one-time election to sell and/or transfer debt securities classified as held-to-maturity may be made at any time after March 12, 2020. The Company anticipates this ASU will simplify any modifications it executes between the selected start date (yet to be determined) and December 31, 2022 that are directly related to the LIBOR transition by allowing prospective recognition of the continuation of the contract, rather than extinguishment of the old contract resulting in writing off unamortized fees and costs. ASU 2020-04 is not expected to have a significant impact on the Company’s financial statements.

Income Per Common Share (Tables

Income Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table illustrates the computation of basic and diluted earnings per share: Three Months Ended March 31, 2021 2020 Amount Per Share Amount Amount Per Share Amount (Amounts in thousands, except per share data) Net income $ 133,309 $ 130,848 Basic: Weighted average shares outstanding 92,854 $ 1.44 94,371 $ 1.39 Diluted: Weighted average shares outstanding 92,854 $ 1.44 94,371 $ 1.39

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2021
Investments Debt And Equity Securities [Abstract]
Schedule of Amortized Cost and Fair Value of Investment Securities	The amortized cost and fair value of investment securities were as follows: March 31, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 600,440 $ 2,171 $ (1,192 ) $ 601,419 Mortgage-backed securities 36,945 497 (506 ) 36,936 Total $ 637,385 $ 2,668 $ (1,698 ) $ 638,355 Held to Maturity States and political subdivisions $ 144,517 $ 5,679 $ (41 ) $ 150,155 Collateralized mortgage obligations 76,073 1,584 (106 ) 77,551 Mortgage-backed securities 9,229,057 127,519 (54,680 ) 9,301,896 Total $ 9,449,647 $ 134,782 $ (54,827 ) $ 9,529,602 December 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale Collateralized mortgage obligations $ 611,353 $ 1,601 $ (620 ) $ 612,334 Mortgage-backed securities 39,187 539 (546 ) 39,180 Total $ 650,540 $ 2,140 $ (1,166 ) $ 651,514 Held to Maturity States and political subdivisions $ 166,175 $ 8,341 $ (32 ) $ 174,484 Collateralized mortgage obligations 96,000 1,669 (219 ) 97,450 Mortgage-backed securities 7,629,131 144,710 (6,633 ) 7,767,208 Total $ 7,891,306 $ 154,720 $ (6,884 ) $ 8,039,142
Securities in Continuous Loss Position	Securities with unrealized losses, segregated by length of time, that have been in a continuous loss position were as follows: March 31, 2021 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) Available for Sale Collateralized mortgage obligations $ 141,726 $ (1,181 ) $ 1,722 $ (11 ) $ 143,448 $ (1,192 ) Mortgage-backed securities 5 — 25,049 (506 ) 25,054 (506 ) Total $ 141,731 $ (1,181 ) $ 26,771 $ (517 ) $ 168,502 $ (1,698 ) Held to Maturity States and political subdivisions $ 3,177 $ (41 ) $ — $ — $ 3,177 $ (41 ) Collateralized mortgage obligations 5,583 (58 ) 3,555 (48 ) 9,138 (106 ) Mortgage-backed securities 2,763,743 (54,367 ) 27,136 (313 ) 2,790,879 (54,680 ) Total $ 2,772,503 $ (54,466 ) $ 30,691 $ (361 ) $ 2,803,194 $ (54,827 ) December 31, 2020 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) Available for Sale Collateralized mortgage obligations $ 254,318 $ (608 ) $ 2,230 $ (12 ) $ 256,548 $ (620 ) Mortgage-backed securities 74 — 26,151 (546 ) 26,225 (546 ) Total $ 254,392 $ (608 ) $ 28,381 $ (558 ) $ 282,773 $ (1,166 ) Held to Maturity States and political subdivisions $ 2,746 $ (32 ) $ — $ — $ 2,746 $ (32 ) Collateralized mortgage obligations 26,141 (219 ) — — 26,141 (219 ) Mortgage-backed securities 674,795 (6,283 ) 29,900 (350 ) 704,695 (6,633 ) Total $ 703,682 $ (6,534 ) $ 29,900 $ (350 ) $ 733,582 $ (6,884 )
Investment Securities by Contractual Maturity	The amortized cost and fair value of investment securities at March 31, 2021, by contractual maturity, are shown below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations at any time with or without call or prepayment penalties. Held to Maturity Available for Sale Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) Due in one year or less $ 20,703 $ 20,807 $ — $ — Due after one year through five years 85,425 89,465 — — Due after five years through ten years 30,440 31,740 — — Due after ten years 7,949 8,143 — — Subtotal 144,517 150,155 — — Mortgage-backed securities and collateralized mortgage obligations 9,305,130 9,379,447 637,385 638,355 Total $ 9,449,647 $ 9,529,602 $ 637,385 $ 638,355

Loans and Allowance for Credi_2

Loans and Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2021
Receivables [Abstract]
Types of Loans in Loan Portfolio	The loan portfolio consists of various types of loans and is categorized by major type as follows: March 31, 2021 December 31, 2020 (Dollars in thousands) Residential mortgage loans held for sale $ 20,991 $ 46,777 Commercial and industrial 3,738,274 3,674,200 Real estate: Construction, land development and other land loans 2,031,355 1,956,960 1-4 family residential (includes home equity) 4,843,724 4,710,761 Commercial real estate (includes multi-family residential) 5,858,475 6,078,764 Farmland 401,282 410,931 Agriculture 170,501 170,421 Consumer and other 301,895 355,751 Total loans held for investment, excluding Warehouse Purchase Program 17,345,506 17,357,788 Warehouse Purchase Program 2,272,389 2,842,379 Total loans, including Warehouse Purchase Program $ 19,638,886 $ 20,246,944
Related Party Loans	An analysis of activity with respect to these related party loans is as follows: As of and for the three months ended March 31, 2021 As of and for the year ended December (Dollars in thousands) Beginning balance on January 1 $ 1,732 $ 4,152 New loans — 813 Transfers — — Repayments (87 ) (3,233 ) Ending balance $ 1,645 $ 1,732
Aging Analysis of Past Due Loans	An aging analysis of past due loans, segregated by category of loan, is presented below: March 31, 2021 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 5,086 $ 56 $ 5,142 $ 1,636 $ 2,024,577 $ 2,031,355 Warehouse Purchase Program loans — — — — 2,272,389 2,272,389 Agriculture and agriculture real estate (includes farmland) 369 — 369 534 570,880 571,783 1-4 family (includes home equity) (1) 6,678 32 6,710 11,425 4,846,580 4,864,715 Commercial real estate (includes multi-family residential) 22,455 225 22,680 16,671 5,819,124 5,858,475 Commercial and industrial 9,485 — 9,485 11,208 3,717,581 3,738,274 Consumer and other 872 — 872 1,551 299,472 301,895 Total $ 44,945 $ 313 $ 45,258 $ 43,025 $ 19,550,603 $ 19,638,886 December 31, 2020 Loans Past Due and Still Accruing 30-89 Days 90 or More Days Total Past Due Loans Nonaccrual Loans Current Loans Total Loans (Dollars in thousands) Construction, land development and other land loans $ 14,820 $ 236 $ 15,056 $ 1,262 $ 1,940,642 $ 1,956,960 Warehouse Purchase Program loans — — — — 2,842,379 2,842,379 Agriculture and agriculture real estate (includes farmland) 538 — 538 1,344 579,470 581,352 1-4 family (includes home equity) (1) 7,527 36 7,563 15,999 4,733,976 4,757,538 Commercial real estate (includes multi-family residential) 17,039 1,409 18,448 10,906 6,049,410 6,078,764 Commercial and industrial 14,383 — 14,383 16,084 3,643,733 3,674,200 Consumer and other 380 18 398 1,590 353,763 355,751 Total $ 54,687 $ 1,699 $ 56,386 $ 47,185 $ 20,143,373 $ 20,246,944 (1) Includes $21.0 million and $46.8 million of residential mortgage loans held for sale at March 31, 2021 and December 31, 2020, respectively.
Non-performing Assets	The following table presents information regarding nonperforming assets as of the dates indicated: March 31, 2021 December 31, 2020 (Dollars in thousands) Nonaccrual loans (1) (2) $ 43,025 $ 47,185 Accruing loans 90 or more days past due 313 1,699 Total nonperforming loans 43,338 48,884 Repossessed assets 362 93 Other real estate 462 10,593 Total nonperforming assets $ 44,162 $ 59,570 Nonperforming assets to total loans and other real estate 0.22 % 0.29 % Nonperforming assets to total loans, excluding Warehouse Purchase Program loans, and other real estate 0.25 % 0.34 % (1) Includes troubled debt restructurings of $8.7 million and $11.3 million as of March 31, 2021 and December 31, 2020, respectively. (2) There were no nonperforming or troubled debt restructurings of warehouse lines of credit or Warehouse Purchase Program loans for the periods presented.
Recorded Investment and Outstanding Balance for Purchased Credit Deteriorated Loans and Non Purchased Credit Deteriorated Loans	The recorded investment in PCD loans included in the consolidated balance sheet and the related outstanding balance as of the dates indicated are presented in the table below. The outstanding balance represents the total amount owed as of March 31, 2021 and December 31, 2020 . March 31, 2021 December 31, 2020 (Dollars in thousands) PCD loans: Outstanding balance $ 163,191 $ 195,631 Discount (11,157 ) (14,216 ) Recorded investment $ 152,034 $ 181,415 March 31, 2021 December 31, 2020 (Dollars in thousands) Non-PCD loans: Outstanding balance $ 3,339,670 $ 3,869,205 Discount (26,285 ) (39,587 ) Recorded investment $ 3,313,385 $ 3,829,618
Summary of Changes in Accretable Yields of Acquired Loans	Changes in the accretable yield for acquired PCD loans for the three months ended March 31, 2021 and 2020 were as follows: Three Months Ended March 31, 2021 2020 (Dollars in thousands) Balance at beginning of period $ 14,216 $ 35,654 Adjustments — (175 ) Accretion charge-offs (32 ) — Accretion (3,027 ) (6,019 ) Balance at March 31, $ 11,157 $ 29,460 Changes in the discount accretion for Non-PCD loans for the three months ended March 31, 2021 and 2020 were as follows: Three Months Ended March 31, 2021 2020 (Dollars in thousands) Balance at beginning of period $ 39,587 $ 110,130 Adjustments — — Accretion charge-offs 11 (54 ) Accretion (13,313 ) (22,463 ) Balance at March 31, $ 26,285 $ 87,613
Risk Grade by Category of Loan and Year of Origination/Renewal	The following tables present loans by risk grade, by category of loan and year of origination/renewal at March 31, 2021. Term Loans Amortized Cost Basis by Origination Year 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Construction, Land Development and Other Land Loans Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 — — — — 83 175 — — 258 Grade 3 175,067 777,262 382,469 116,663 135,436 54,457 123,027 — 1,764,381 Grade 4 3,127 89,839 91,719 29,032 8,761 9,294 11,335 — 243,107 Grade 5 2,625 11,729 491 813 76 112 — — 15,846 Grade 6 — 4,442 — — — 1,192 — — 5,634 Grade 7 — 397 — 1,179 — 59 — — 1,635 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — — 154 102 238 — — — 494 Total $ 180,819 $ 883,669 $ 474,833 $ 147,789 $ 144,594 $ 65,289 $ 134,362 $ — $ 2,031,355 Agriculture and Agriculture Real Estate (includes Farmland) Grade 1 $ 463 $ 1,532 $ 377 $ 161 $ 174 $ — $ 8,785 $ 90 $ 11,582 Grade 2 — 10 — — 344 1,393 23 — 1,770 Grade 3 23,622 116,759 64,809 51,000 35,448 118,139 79,549 — 489,326 Grade 4 5,365 11,268 3,883 5,227 2,869 20,396 10,055 8 59,071 Grade 5 — 2,386 568 98 — — 2,538 — 5,590 Grade 6 — 1,281 42 59 — 836 — — 2,218 Grade 7 — 146 61 4 — 322 — — 533 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — 955 193 274 — 271 — — 1,693 Total $ 29,450 $ 134,337 $ 69,933 $ 56,823 $ 38,835 $ 141,357 $ 100,950 $ 98 $ 571,783 1-4 Family (includes Home Equity) (1) Grade 1 $ — $ 116 $ — $ — $ — $ — $ — $ — $ 116 Grade 2 77 415 306 874 433 6,741 950 — 9,796 Grade 3 396,356 1,408,886 778,786 508,016 389,576 1,099,044 115,347 1,530 4,697,541 Grade 4 4,588 11,960 21,366 25,480 26,267 46,169 2,605 — 138,435 Grade 5 — 315 318 154 501 2,438 247 — 3,973 Grade 6 — 21 65 2 2 2,405 — — 2,495 Grade 7 — 115 989 1,699 2,483 5,532 — — 10,818 Grade 8 — — — — — 38 — — 38 Grade 9 — — — — — — — — — PCD Loans — — — — — 1,503 — — 1,503 Total $ 401,021 $ 1,421,828 $ 801,830 $ 536,225 $ 419,262 $ 1,163,870 $ 119,149 $ 1,530 $ 4,864,715 Term Loans Amortized Cost Basis by Origination Year 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Commercial Real Estate (includes Multi-Family Residential) Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 596 8,826 1,444 — 6,937 1,069 — — 18,872 Grade 3 135,632 682,123 815,581 799,073 592,083 1,217,452 90,900 2,425 4,335,269 Grade 4 32,617 121,746 120,200 186,136 194,686 384,973 7,710 — 1,048,068 Grade 5 — 47,109 15,471 53,977 25,264 143,502 2,305 — 287,628 Grade 6 — 20,451 166 1,238 22,159 33,684 — — 77,698 Grade 7 — 16 — 1,201 14 9,335 1,439 — 12,005 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 35,636 25,238 6,649 664 — 10,748 — — 78,935 Total $ 204,481 $ 905,509 $ 959,511 $ 1,042,289 $ 841,143 $ 1,800,763 $ 102,354 $ 2,425 $ 5,858,475 Commercial and Industrial Grade 1 $ 543,536 $ 610,253 $ 3,274 $ 3,138 $ 678 $ 799 $ 22,920 $ 160 $ 1,184,758 Grade 2 1,398 970 8,631 510 1,085 2,153 8,504 — 23,251 Grade 3 227,659 379,975 265,630 199,222 91,252 169,696 705,395 917 2,039,746 Grade 4 7,334 54,622 58,081 47,689 9,982 17,124 140,212 975 336,019 Grade 5 33 10,735 19,074 4,655 1,408 85 7,943 81 44,014 Grade 6 451 1,792 74 168 61 3,513 8,426 — 14,485 Grade 7 163 462 288 7,710 141 1,160 20,163 — 30,087 Grade 8 — — — — — 5 — — 5 Grade 9 — — — — — — — — — PCD Loans — 41,441 808 11,170 10,131 108 2,251 — 65,909 Total $ 780,574 $ 1,100,250 $ 355,860 $ 274,262 $ 114,738 $ 194,643 $ 915,814 $ 2,133 $ 3,738,274 Consumer and Other Grade 1 $ 5,968 $ 26,100 $ 6,637 $ 2,683 $ 1,903 $ 1,150 $ 1,496 $ — $ 45,937 Grade 2 — 1,267 621 384 30,443 1,429 537 — 34,681 Grade 3 20,551 36,543 37,667 22,455 10,995 11,321 49,164 — 188,696 Grade 4 8 5,786 128 340 72 141 10,947 — 17,422 Grade 5 — 14 — 63 17 — — — 94 Grade 6 — — — — — — 9,997 — 9,997 Grade 7 — — 1,529 14 3 22 — — 1,568 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — 3,500 — — — — — — 3,500 Total $ 26,527 $ 73,210 $ 46,582 $ 25,939 $ 43,433 $ 14,063 $ 72,141 $ — $ 301,895 Term Loans Amortized Cost Basis by Origination Year 2021 2020 2019 2018 2017 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Warehouse Purchase Program Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 — — — — — — — — — Grade 3 2,272,389 — — — — — — — 2,272,389 Grade 4 — — — — — — — — — Grade 5 — — — — — — — — — Grade 6 — — — — — — — — — Grade 7 — — — — — — — — — Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — — — — — — — — — Total $ 2,272,389 $ — $ — $ — $ — $ — $ — $ — $ 2,272,389 Total Grade 1 $ 549,967 $ 638,001 $ 10,288 $ 5,982 $ 2,755 $ 1,949 $ 33,201 $ 250 $ 1,242,393 Grade 2 2,071 11,488 11,002 1,768 39,325 12,960 10,014 — 88,628 Grade 3 3,251,276 3,401,548 2,344,942 1,696,429 1,254,790 2,670,109 1,163,382 4,872 15,787,348 Grade 4 53,039 295,221 295,377 293,904 242,637 478,097 182,864 983 1,842,122 Grade 5 2,658 72,288 35,922 59,760 27,266 146,137 13,033 81 357,145 Grade 6 451 27,987 347 1,467 22,222 41,630 18,423 — 112,527 Grade 7 163 1,136 2,867 11,807 2,641 16,430 21,602 — 56,646 Grade 8 — — — — — 43 — — 43 Grade 9 — — — — — — — — — PCD Loans 35,636 71,134 7,804 12,210 10,369 12,630 2,251 — 152,034 Total $ 3,895,261 $ 4,518,803 $ 2,708,549 $ 2,083,327 $ 1,602,005 $ 3,379,985 $ 1,444,770 $ 6,186 $ 19,638,886 (1) Includes $21.0 million of residential mortgage loans held for sale at March 31, 2021.
Allowance for Credit Losses on Loans by Category of Loan	The following table details activity in the allowance for credit losses on loans by category of loan for the three months ended March 31, 2021 and 2020. Construction, Land Development and Other Land Loans Agriculture and Agriculture Real Estate (includes Farmland) 1-4 Family (includes Home Equity) Commercial Real Estate (includes Multi-Family Residential) Commercial and Industrial Consumer and Other Total (Dollars in thousands) Allowance for credit losses: Three Months Ended Balance December 31, 2020 $ 44,892 $ 7,824 $ 44,555 $ 87,857 $ 116,795 $ 14,145 $ 316,068 Provision for credit losses 5,221 312 3,194 4,572 (9,816 ) (3,483 ) — Charge-offs — (38 ) (54 ) (6,589 ) (1,754 ) (935 ) (9,370 ) Recoveries 5 5 7 — 170 325 512 Net charge-offs 5 (33 ) (47 ) (6,589 ) (1,584 ) (610 ) (8,858 ) Balance March 31, 2021 $ 50,118 $ 8,103 $ 47,702 $ 85,840 $ 105,395 $ 10,052 $ 307,210 Allowance for credit losses: Three Months Ended Balance December 31, 2019 $ 14,654 $ 2,971 $ 15,277 $ 12,332 $ 40,445 $ 1,790 $ 87,469 Impact of adoption ASU 2016-13 14,075 2,797 8,267 48,990 139,624 26,785 240,538 Provision for credit losses — — — — — — — Charge-offs — (31 ) (29 ) — (611 ) (1,316 ) (1,987 ) Recoveries 12 32 24 81 639 398 1,186 Net charge-offs 12 1 (5 ) 81 28 (918 ) (801 ) Balance March 31, 2020 $ 28,741 $ 5,769 $ 23,539 $ 61,403 $ 180,097 $ 27,657 $ 327,206

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Assets and Liabilities Measured on Recurring Basis	The following tables present fair values for assets and liabilities measured at fair value on a recurring basis: As of March 31, 2021 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: Collateralized mortgage obligations $ — $ 601,419 $ — $ 601,419 Mortgage-backed securities — 36,936 — 36,936 Total $ — $ 638,355 $ — $ 638,355 Derivative financial instruments: Loan customer counterparty $ — $ 8,881 $ — $ 8,881 Financial institution counterparty — — — — Liabilities: Derivative financial instruments: Loan customer counterparty $ — $ — $ — $ — Financial institution counterparty — 8,881 — 8,881 As of December 31, 2020 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: Collateralized mortgage obligations $ — $ 612,334 $ — $ 612,334 Mortgage-backed securities — 39,180 — 39,180 Total available for sale securities $ — $ 651,514 $ — $ 651,514 Derivative financial instruments: Loan customer counterparty — 11,912 — 11,912 Financial institution counterparty — — — — Liabilities: Derivative financial instruments: Loan customer counterparty — — — — Financial institution counterparty — 11,912 — 11,912
Summary of Carrying and Fair Value Information of Financial Instruments	The following tables present carrying and fair value information of financial instruments as of the dates indicated: As of March 31, 2021 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 1,947,235 $ 1,947,235 $ — $ — $ 1,947,235 Federal funds sold 8,986 8,986 — — 8,986 Held to maturity securities 9,449,647 — 9,529,602 — 9,529,602 Loans held for sale 20,991 — 20,991 — 20,991 Loans held for investment, net of allowance 17,038,296 — — 17,137,592 17,137,592 Loans held for investment - Warehouse Purchase Program 2,272,389 — 2,272,389 — 2,272,389 Other real estate owned 462 — 462 — 462 Liabilities Deposits: Noninterest-bearing $ 9,820,445 $ — $ 9,820,445 $ — $ 9,820,445 Interest-bearing 18,942,660 — 18,954,529 — 18,954,529 Securities sold under repurchase agreements 377,106 — 377,115 — 377,115 As of December 31, 2020 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 1,342,996 $ 1,342,996 $ — $ — $ 1,342,996 Federal funds sold 553 553 — — 553 Held to maturity securities 7,891,306 — 8,039,142 — 8,039,142 Loans held for sale 46,777 — 46,777 — 46,777 Loans held for investment, net of allowance 17,041,720 — — 17,118,745 17,118,745 Loans held for investment - Warehouse Purchase Program 2,842,379 — 2,842,379 — 2,842,379 Other real estate owned 10,593 — 10,593 — 10,593 Liabilities Deposits: Noninterest-bearing $ 9,151,233 $ — $ 9,151,233 $ — $ 9,151,233 Interest-bearing 18,209,259 — 18,227,623 — 18,227,623 Securities sold under repurchase agreements 389,583 — 389,595 — 389,595

Goodwill and Core Deposit Int_2

Goodwill and Core Deposit Intangibles (Tables)	3 Months Ended
	Mar. 31, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Core Deposit Intangibles	Changes in the carrying amount of the Company’s goodwill and core deposit intangibles for the three months ended March 31, 2021 and the year ended December 31, 2020 were as follows: Goodwill Core Deposit Intangibles (Dollars in thousands) Balance as of December 31, 2019 $ 3,223,671 $ 86,404 Less: Amortization — (13,169 ) Add: Measurement period adjustment of LegacyTexas Merger ( 1) 7,965 — Balance as of December 31, 2020 3,231,636 73,235 Less: Amortization — (2,931 ) Balance as of March 31, 2021 $ 3,231,636 $ 70,304 (1) LegacyTexas Financial Group, Inc. (“LegacyTexas”) merged into Bancshares on November 1, 2019.
Estimated Aggregate Future Amortization Expense for Core Deposit Intangibles	The estimated aggregate future amortization expense for core deposit intangibles remaining as of March 31, 2021 is as follows (dollars in thousands): Remaining 2021 $ 8,621 2022 10,336 2023 9,360 2024 8,699 2025 8,173 Thereafter 25,115 Total $ 70,304

Contractual Obligations and O_2

Contractual Obligations and Off-Balance Sheet Items (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Future Undiscounted Cash Payments Associated with its Operating Leases	The Company’s future undiscounted cash payments associated with its operating leases as of March 31, 2021 are summarized below (dollars in thousands). Remaining 2021 $ 8,305 2022 10,608 2023 9,860 2024 8,938 2025 8,546 2026 7,853 Thereafter 12,716 Total undiscounted lease payments $ 66,826
Summary of Commitments Associated with Outstanding Standby Letters of Credit, Unused Capacity on Warehouse Purchase Program Loans and Commitments to Extend Credit	The Company’s commitments associated with outstanding standby letters of credit, unused capacity on Warehouse Purchase Program loans and commitments to extend credit expiring by period as of March 31, 2021 are summarized below. Since commitments associated with letters of credit, unused capacity of Warehouse Purchase Program loans and commitments to extend credit may expire unused, the amounts shown do not necessarily reflect the actual future cash funding requirements. 1 year or less More than 1 year but less than 3 years 3 years or more but less than 5 years 5 years or more Total (Dollars in thousands) Standby letters of credit $ 96,944 $ 6,133 $ 803 $ — $ 103,880 Unused capacity on Warehouse Purchase Program loans 1,500,611 — — — 1,500,611 Commitments to extend credit 1,713,071 779,833 369,880 1,127,890 3,990,674 Total $ 3,310,626 $ 785,966 $ 370,683 $ 1,127,890 $ 5,595,165

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Tax Effects Allocated to Each Component of Other Comprehensive Income	The tax effects allocated to each component of other comprehensive income were as follows: Three Months Ended March 31, 2021 2020 Before Tax Amount Tax Effect Net of Tax Amount Before Tax Amount Tax Effect Net of Tax Amount (Dollars in thousands) Other comprehensive loss: Securities available for sale: Change in unrealized loss during period $ (4 ) $ 1 $ (3 ) $ (4,183 ) $ 878 $ (3,305 ) Total securities available for sale (4 ) 1 (3 ) (4,183 ) 878 (3,305 ) Total other comprehensive loss $ (4 ) $ 1 $ (3 ) $ (4,183 ) $ 878 $ (3,305 )
Activity in Accumulated Other Comprehensive Income Associated with Securities Available for Sale, Net of Tax	Activity in accumulated other comprehensive income associated with securities available for sale, net of tax, was as follows: Securities Available for Sale Accumulated Other Comprehensive Income (Loss) (Dollars in thousands) Balance at December 31, 2020 $ 769 $ 769 Other comprehensive loss (3 ) (3 ) Balance at March 31, 2021 $ 766 $ 766 Balance at December 31, 2019 $ 602 $ 602 Other comprehensive loss (3,305 ) (3,305 ) Balance at March 31, 2020 $ (2,703 ) $ (2,703 )

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2021
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Notional Balances and Fair Value of Derivative Positions	The following table provides the outstanding notional balances and fair values of outstanding derivative positions at March 31, 2021 and December 31, 2020. March 31, 2021 December 31, 2020 Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value (Dollars in thousands) Commercial loan interest rate swaps and caps: Loan customer counterparty $ 249,433 $ 8,881 $ — $ 224,684 $ 11,912 $ — Financial institution counterparty 249,433 — 8,881 224,684 — 11,912
Schedule of Weighted Average Received and Paid Interest Rates for Interest Rate Swaps Outstanding	The commercial loan customer counterparty weighted average received and paid interest rates for interest rate swaps outstanding at March 31, 2021 and December 31, 2020 are presented in the following table. Weighted-Average Interest Rate March 31, 2021 December 31, 2020 Received Paid Received Paid Loan customer counterparty 2.62 % 0.68 % 2.83 % 0.79 %
Schedule of Income (Loss) from Derivatives Not Designated as Hedging Instruments	Income (loss) for the three months ended March 31, 2021 and 20 20 was as follows: Three Months Ended March 31, Derivatives not designated as hedging instruments 2021 2020 (Dollars in thousands) Interest rate lock commitments $ — $ 1,112 Forward mortgage-backed securities trades — (1,937 )

Income Per Common Share - Sched

Income Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income	$ 133,309	$ 130,848
Basic, Weighted average shares outstanding (in shares)	92,854	94,371
Basic	$ 1.44	$ 1.39
Diluted, Weighted average shares outstanding (in shares)	92,854	94,371
Diluted	$ 1.44	$ 1.39

Income Per Common Share - Addit

Income Per Common Share - Additional Information (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Number of options outstanding	0	0
Antidilutive Securities excluded from computation of earnings per share, amount	0	0

Securities - Schedule of Amorti

Securities - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	$ 637,385	$ 650,540
Available for Sale, Gross Unrealized Gains	2,668	2,140
Available for Sale, Gross Unrealized Losses	(1,698)	(1,166)
Available for Sale	638,355	651,514
Held to Maturity, Amortized Cost	9,449,647	7,891,306
Held to Maturity, Gross Unrealized Gains	134,782	154,720
Held to Maturity, Gross Unrealized Losses	(54,827)	(6,884)
Held to Maturity	9,529,602	8,039,142
States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, Amortized Cost	144,517	166,175
Held to Maturity, Gross Unrealized Gains	5,679	8,341
Held to Maturity, Gross Unrealized Losses	(41)	(32)
Held to Maturity	150,155	174,484
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	600,440	611,353
Available for Sale, Gross Unrealized Gains	2,171	1,601
Available for Sale, Gross Unrealized Losses	(1,192)	(620)
Available for Sale	601,419	612,334
Held to Maturity, Amortized Cost	76,073	96,000
Held to Maturity, Gross Unrealized Gains	1,584	1,669
Held to Maturity, Gross Unrealized Losses	(106)	(219)
Held to Maturity	77,551	97,450
Mortgage-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	36,945	39,187
Available for Sale, Gross Unrealized Gains	497	539
Available for Sale, Gross Unrealized Losses	(506)	(546)
Available for Sale	36,936	39,180
Held to Maturity, Amortized Cost	9,229,057	7,629,131
Held to Maturity, Gross Unrealized Gains	127,519	144,710
Held to Maturity, Gross Unrealized Losses	(54,680)	(6,633)
Held to Maturity	$ 9,301,896	$ 7,767,208

Securities - Additional Informa

Securities - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)SegmentSecurity	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)Security
Schedule Of Held To Maturity Securities [Line Items]
Number of Investment Securities Segments | Segment	2
Credit losses	$ 0
Municipal securities percentage of securities portfolio	1.40%
Securities in Unrealized Loss Positions Qualitative Disclosure Number of Positions Greater Than or Equal to One Year | Security	74		64
Gain (loss) on sale of securities	$ 0	$ 0
Available for sale securities, at fair value	638,355,000		$ 651,514,000
Collateralized Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	6,930,000,000		6,110,000,000
Available for sale securities, at fair value	$ 7,020,000,000		$ 6,230,000,000
Securities Concentration Risk [Member] | Stockholders' Equity, Total [Member]
Schedule Of Held To Maturity Securities [Line Items]
Concentration Risk, Percentage	10.00%		10.00%

Securities - Securities in Cont

Securities - Securities in Continuous Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	$ 141,731	$ 254,392
Available for Sale, Unrealized Losses, Less than 12 Months	(1,181)	(608)
Available for Sale, Estimated Fair Value, 12 Months or More	26,771	28,381
Available for Sale, Unrealized Losses, 12 Months or More	(517)	(558)
Available for Sale, Estimated Fair Value, Total	168,502	282,773
Available for Sale, Unrealized Losses, Total	(1,698)	(1,166)
Held to Maturity, Estimated Fair Value, Less than 12 Months	2,772,503	703,682
Held to Maturity, Unrealized Losses, Less than 12 Months	(54,466)	(6,534)
Held to Maturity, Estimated Fair Value, 12 Months or More	30,691	29,900
Held to Maturity, Unrealized Losses, 12 Months or More	(361)	(350)
Held to Maturity, Estimated Fair Value, Total	2,803,194	733,582
Held to Maturity, Unrealized Losses, Total	(54,827)	(6,884)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	141,726	254,318
Available for Sale, Unrealized Losses, Less than 12 Months	(1,181)	(608)
Available for Sale, Estimated Fair Value, 12 Months or More	1,722	2,230
Available for Sale, Unrealized Losses, 12 Months or More	(11)	(12)
Available for Sale, Estimated Fair Value, Total	143,448	256,548
Available for Sale, Unrealized Losses, Total	(1,192)	(620)
Held to Maturity, Estimated Fair Value, Less than 12 Months	5,583	26,141
Held to Maturity, Unrealized Losses, Less than 12 Months	(58)	(219)
Held to Maturity, Estimated Fair Value, 12 Months or More	3,555
Held to Maturity, Unrealized Losses, 12 Months or More	(48)
Held to Maturity, Estimated Fair Value, Total	9,138	26,141
Held to Maturity, Unrealized Losses, Total	(106)	(219)
Mortgage-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	5	74
Available for Sale, Estimated Fair Value, 12 Months or More	25,049	26,151
Available for Sale, Unrealized Losses, 12 Months or More	(506)	(546)
Available for Sale, Estimated Fair Value, Total	25,054	26,225
Available for Sale, Unrealized Losses, Total	(506)	(546)
Held to Maturity, Estimated Fair Value, Less than 12 Months	2,763,743	674,795
Held to Maturity, Unrealized Losses, Less than 12 Months	(54,367)	(6,283)
Held to Maturity, Estimated Fair Value, 12 Months or More	27,136	29,900
Held to Maturity, Unrealized Losses, 12 Months or More	(313)	(350)
Held to Maturity, Estimated Fair Value, Total	2,790,879	704,695
Held to Maturity, Unrealized Losses, Total	(54,680)	(6,633)
States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, Estimated Fair Value, Less than 12 Months	3,177	2,746
Held to Maturity, Unrealized Losses, Less than 12 Months	(41)	(32)
Held to Maturity, Estimated Fair Value, Total	3,177	2,746
Held to Maturity, Unrealized Losses, Total	$ (41)	$ (32)

Securities - Investment Securit

Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Held to Maturity, amortized cost, due in one year or less	$ 20,703
Held to Maturity, amortized cost, due after one year through five years	85,425
Held to Maturity, amortized cost, due after five years through ten years	30,440
Held to Maturity, amortized cost, due after ten years	7,949
Held to Maturity, amortized cost, subtotal	144,517
Held to Maturity, amortized cost, mortgage-backed securities and collateralized mortgage obligations	9,305,130
Held to Maturity, Amortized Cost	9,449,647	$ 7,891,306
Held to Maturity, fair value, due in one year or less	20,807
Held to Maturity, fair value, due after one year through five years	89,465
Held to Maturity, fair value, due after five years through ten years	31,740
Held to Maturity, fair value, due after ten years	8,143
Held to Maturity, fair value, subtotal	150,155
Held to Maturity, fair value, mortgage-backed securities and collateralized mortgage obligations	9,379,447
Held to Maturity, fair value, total	9,529,602	8,039,142
Available for Sale, amortized cost, mortgage-backed securities and collateralized mortgage obligations	637,385
Available for Sale, Amortized Cost	637,385	650,540
Available for Sale, fair value, mortgage-backed securities and collateralized mortgage obligations	638,355
Available for Sale securities, at fair value	$ 638,355	$ 651,514

Loans and Allowance for Credi_3

Loans and Allowance for Credit Losses - Types of Loans in Loan Portfolio (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale		$ 20,991	$ 46,777
Total loans held for investment		17,345,506	17,357,788
Total loans, including Warehouse Purchase Program		19,638,886	20,246,944
Residential Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale		20,991	46,777
Warehouse Purchase Program [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		2,272,389	2,842,379
Total loans, including Warehouse Purchase Program		2,272,389	2,842,379
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		3,738,274	3,674,200
Total loans, including Warehouse Purchase Program		3,738,274	3,674,200
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		2,031,355	1,956,960
Total loans, including Warehouse Purchase Program		2,031,355	1,956,960
Real Estate [Member] | 1-4 Family [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		4,843,724	4,710,761
Total loans, including Warehouse Purchase Program	[1]	4,864,715	4,757,538
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		5,858,475	6,078,764
Total loans, including Warehouse Purchase Program		5,858,475	6,078,764
Real Estate [Member] | Farmland [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		401,282	410,931
Agriculture [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		170,501	170,421
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		301,895	355,751
Total loans, including Warehouse Purchase Program		$ 301,895	$ 355,751
[1]	Includes $21.0 million and $46.8 million of residential mortgage loans held for sale at March 31, 2021 and December 31, 2020, respectively.

Loans and Allowance for Credi_4

Loans and Allowance for Credit Losses - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)contract	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Accounts Notes And Loans Receivable [Line Items]
Percentage of Loans Related to Single Industry on Loans	10.00%		10.00%
Percentage of real estate loans aggregating to company loan portfolio, excluding Warehouse Purchase Program loans	73.30%
Loans and Leases Receivable, Related Parties	$ 1,645		$ 1,732	$ 4,152
Loans held for investment	$ 17,345,506		$ 17,357,788
Financing Receivable Ratio of Nonperforming Loans to All Loans and Other Real Estate	0.22%		0.29%
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 982	$ 869
Loans and leases receivable, nonaccrual loans	43,000	58,200
Financing Receivable, Allowance for Credit Losses on Loans	$ 307,200		$ 316,100
Allowance for Credit Losses as Percentage of Loans	1.56%		1.56%
Decrease in allowance for credit losses for loans	$ 8,900
Decrease in allowance for credit losses for loans, percentage	2.80%
Net charge-offs	$ 8,858	801
Allowance for credit losses on off-balance sheet credit exposures	29,947		$ 29,947
Commitments expected to fund	1,640,000
Nonaccrual loans	$ 43,025		47,185
Financing receivable, number of loans with default | contract	0
Loan to be Considered as Payment Default in Period	90 days
Outstanding loan on deferral and modification agreements	$ 316,700
Troubled Debt Restructuring [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit losses on off-balance sheet credit exposures	29,900		29,900
Nonaccrual loans	8,700	$ 13,000
PCD Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Net charge-offs	7,100
Additional specific reserves	4,200
CARES Act [Member] | Paycheck Protection Program [Member]
Accounts Notes And Loans Receivable [Line Items]
Funded amount	1,140,000
Nonperforming Financial Instruments [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 44,200		$ 59,600

Loans and Allowance for Credi_5

Loans and Allowance for Credit Losses - Related Party Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Receivables [Abstract]
Beginning balance on January 1	$ 1,732	$ 4,152
New loans		813
Repayments	(87)	(3,233)
Ending balance	$ 1,645	$ 1,732

Loans and Allowance for Credi_6

Loans and Allowance for Credit Losses - Aging Analysis of Past Due Loans (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		$ 45,258	$ 56,386
Nonaccrual loans		43,025	47,185
Current loans		19,550,603	20,143,373
Total loans		19,638,886	20,246,944
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		44,945	54,687
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		313	1,699
Warehouse Purchase Program Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Current loans		2,272,389	2,842,379
Total loans		2,272,389	2,842,379
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		369	538
Nonaccrual loans		534	1,344
Current loans		570,880	579,470
Total loans		571,783	581,352
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		369	538
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		5,142	15,056
Nonaccrual loans		1,636	1,262
Current loans		2,024,577	1,940,642
Total loans		2,031,355	1,956,960
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		5,086	14,820
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		56	236
Real Estate [Member] | 1-4 Family Residential (Includes Home Equity) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing	[1]	6,710	7,563
Nonaccrual loans	[1]	11,425	15,999
Current loans	[1]	4,846,580	4,733,976
Total loans	[1]	4,864,715	4,757,538
Real Estate [Member] | 1-4 Family Residential (Includes Home Equity) [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing	[1]	6,678	7,527
Real Estate [Member] | 1-4 Family Residential (Includes Home Equity) [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing	[1]	32	36
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		22,680	18,448
Nonaccrual loans		16,671	10,906
Current loans		5,819,124	6,049,410
Total loans		5,858,475	6,078,764
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		22,455	17,039
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		225	1,409
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		9,485	14,383
Nonaccrual loans		11,208	16,084
Current loans		3,717,581	3,643,733
Total loans		3,738,274	3,674,200
Commercial and Industrial [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		9,485	14,383
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		872	398
Nonaccrual loans		1,551	1,590
Current loans		299,472	353,763
Total loans		301,895	355,751
Consumer and Other [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		$ 872	380
Consumer and Other [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing			$ 18
[1]	Includes $21.0 million and $46.8 million of residential mortgage loans held for sale at March 31, 2021 and December 31, 2020, respectively.

Loans and Allowance for Credi_7

Loans and Allowance for Credit Losses - Aging Analysis of Past Due Loans (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	$ 20,991	$ 46,777
Residential Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	$ 20,991	$ 46,777

Loans and Allowance for Credi_8

Loans and Allowance for Credit Losses - Nonperforming Assets (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 17,345,506	$ 17,357,788
Other real estate owned		$ 462	$ 10,593
Nonperforming assets to total loans and other real estate		0.22%	0.29%
Nonperforming assets to total loans, excluding Warehouse Purchase Program loans, and other real estate		0.25%	0.34%
Nonperforming Financial Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 43,338	$ 48,884
Repossessed assets		362	93
Other real estate owned		462	10,593
Total nonperforming assets		44,162	59,570
Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	[1],[2]	43,025	47,185
Nonperforming Financial Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 313	$ 1,699
[1]	Includes troubled debt restructurings of $8.7 million and $11.3 million as of March 31, 2021 and December 31, 2020, respectively.
[2]	There were no nonperforming or troubled debt restructurings of warehouse lines of credit or Warehouse Purchase Program loans for the periods presented.

Loans and Allowance for Credi_9

Loans and Allowance for Credit Losses - Nonperforming Assets (Parenthetical) (Details) - USD ($)		Mar. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 17,345,506,000	$ 17,357,788,000
Nonperforming Financial Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		43,338,000	48,884,000
Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	[1],[2]	43,025,000	47,185,000
Troubled Debt Restructuring [Member] | Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		8,700,000	11,300,000
Troubled Debt Restructuring [Member] | Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member] | Warehouse Purchase Program [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 0	$ 0
[1]	Includes troubled debt restructurings of $8.7 million and $11.3 million as of March 31, 2021 and December 31, 2020, respectively.
[2]	There were no nonperforming or troubled debt restructurings of warehouse lines of credit or Warehouse Purchase Program loans for the periods presented.

Loans and Allowance for Cred_10

Loans and Allowance for Credit Losses - Recorded Investment and Outstanding Balance for Purchased Credit Deteriorated Loans and Non Purchased Credit Deteriorated Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
PCD Loans [Member]
Purchased And Non Purchased Credit Impaired Loans [Line Items]
Outstanding balance	$ 163,191	$ 195,631
Discount	(11,157)	(14,216)
Recorded investment	152,034	181,415
Non-PCD Loans [Member]
Purchased And Non Purchased Credit Impaired Loans [Line Items]
Outstanding balance	3,339,670	3,869,205
Discount	(26,285)	(39,587)
Recorded investment	$ 3,313,385	$ 3,829,618

Loans and Allowance for Cred_11

Loans and Allowance for Credit Losses - Summary of Changes in Accretable Yields of Acquired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
PCD Loans [Member]
Changes In Accretable Yield for PCI And Non PCI Loans [Line Items]
Balance at beginning of period	$ 14,216	$ 35,654
Adjustments		(175)
Accretion charge-offs	(32)
Accretion	(3,027)	(6,019)
Balance at March 31,	11,157	29,460
Non-PCD Loans [Member]
Changes In Accretable Yield for PCI And Non PCI Loans [Line Items]
Balance at beginning of period	39,587	110,130
Accretion charge-offs	11	(54)
Accretion	(13,313)	(22,463)
Balance at March 31,	$ 26,285	$ 87,613

Loans and Allowance for Cred_12

Loans and Allowance for Credit Losses - Risk Grade by Category of Loan and Year of Origination/Renewal (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Financing Receivable Impaired [Line Items]
2021		$ 3,895,261
2020		4,518,803
2019		2,708,549
2018		2,083,327
2017		1,602,005
Prior		3,379,985
Revolving Loans		1,444,770
Revolving Loans Converted to Term Loans		6,186
Total loans		19,638,886	$ 20,246,944
PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2021		35,636
2020		71,134
2019		7,804
2018		12,210
2017		10,369
Prior		12,630
Revolving Loans		2,251
Total loans		152,034
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2021		29,450
2020		134,337
2019		69,933
2018		56,823
2017		38,835
Prior		141,357
Revolving Loans		100,950
Revolving Loans Converted to Term Loans		98
Total loans		571,783	581,352
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020		955
2019		193
2018		274
Prior		271
Total loans		1,693
Warehouse Purchase Program [Member]
Financing Receivable Impaired [Line Items]
2021		2,272,389
Total loans		2,272,389	2,842,379
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2021		180,819
2020		883,669
2019		474,833
2018		147,789
2017		144,594
Prior		65,289
Revolving Loans		134,362
Total loans		2,031,355	1,956,960
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2019		154
2018		102
2017		238
Total loans		494
Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2021		401,021
2020		1,421,828
2019		801,830
2018		536,225
2017		419,262
Prior		1,163,870
Revolving Loans		119,149
Revolving Loans Converted to Term Loans		1,530
Total loans	[1]	4,864,715	4,757,538
Real Estate [Member] | 1-4 Family [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
Prior		1,503
Total loans		1,503
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2021		204,481
2020		905,509
2019		959,511
2018		1,042,289
2017		841,143
Prior		1,800,763
Revolving Loans		102,354
Revolving Loans Converted to Term Loans		2,425
Total loans		5,858,475	6,078,764
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2021		35,636
2020		25,238
2019		6,649
2018		664
Prior		10,748
Total loans		78,935
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		780,574
2020		1,100,250
2019		355,860
2018		274,262
2017		114,738
Prior		194,643
Revolving Loans		915,814
Revolving Loans Converted to Term Loans		2,133
Total loans		3,738,274	3,674,200
Commercial and Industrial [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020		41,441
2019		808
2018		11,170
2017		10,131
Prior		108
Revolving Loans		2,251
Total loans		65,909
Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2021		26,527
2020		73,210
2019		46,582
2018		25,939
2017		43,433
Prior		14,063
Revolving Loans		72,141
Total loans		301,895	$ 355,751
Consumer and Other [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020		3,500
Total loans		3,500
Grade 1 [Member]
Financing Receivable Impaired [Line Items]
2021		549,967
2020		638,001
2019		10,288
2018		5,982
2017		2,755
Prior		1,949
Revolving Loans		33,201
Revolving Loans Converted to Term Loans		250
Total loans		1,242,393
Grade 1 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2021		463
2020		1,532
2019		377
2018		161
2017		174
Revolving Loans		8,785
Revolving Loans Converted to Term Loans		90
Total loans		11,582
Grade 1 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020		116
Total loans		116
Grade 1 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		543,536
2020		610,253
2019		3,274
2018		3,138
2017		678
Prior		799
Revolving Loans		22,920
Revolving Loans Converted to Term Loans		160
Total loans		1,184,758
Grade 1 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2021		5,968
2020		26,100
2019		6,637
2018		2,683
2017		1,903
Prior		1,150
Revolving Loans		1,496
Total loans		45,937
Grade 2 [Member]
Financing Receivable Impaired [Line Items]
2021		2,071
2020		11,488
2019		11,002
2018		1,768
2017		39,325
Prior		12,960
Revolving Loans		10,014
Total loans		88,628
Grade 2 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020		10
2017		344
Prior		1,393
Revolving Loans		23
Total loans		1,770
Grade 2 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2017		83
Prior		175
Total loans		258
Grade 2 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2021		77
2020		415
2019		306
2018		874
2017		433
Prior		6,741
Revolving Loans		950
Total loans		9,796
Grade 2 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2021		596
2020		8,826
2019		1,444
2017		6,937
Prior		1,069
Total loans		18,872
Grade 2 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		1,398
2020		970
2019		8,631
2018		510
2017		1,085
Prior		2,153
Revolving Loans		8,504
Total loans		23,251
Grade 2 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020		1,267
2019		621
2018		384
2017		30,443
Prior		1,429
Revolving Loans		537
Total loans		34,681
Grade 3 [Member]
Financing Receivable Impaired [Line Items]
2021		3,251,276
2020		3,401,548
2019		2,344,942
2018		1,696,429
2017		1,254,790
Prior		2,670,109
Revolving Loans		1,163,382
Revolving Loans Converted to Term Loans		4,872
Total loans		15,787,348
Grade 3 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2021		23,622
2020		116,759
2019		64,809
2018		51,000
2017		35,448
Prior		118,139
Revolving Loans		79,549
Total loans		489,326
Grade 3 [Member] | Warehouse Purchase Program [Member]
Financing Receivable Impaired [Line Items]
2021		2,272,389
Total loans		2,272,389
Grade 3 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2021		175,067
2020		777,262
2019		382,469
2018		116,663
2017		135,436
Prior		54,457
Revolving Loans		123,027
Total loans		1,764,381
Grade 3 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2021		396,356
2020		1,408,886
2019		778,786
2018		508,016
2017		389,576
Prior		1,099,044
Revolving Loans		115,347
Revolving Loans Converted to Term Loans		1,530
Total loans		4,697,541
Grade 3 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2021		135,632
2020		682,123
2019		815,581
2018		799,073
2017		592,083
Prior		1,217,452
Revolving Loans		90,900
Revolving Loans Converted to Term Loans		2,425
Total loans		4,335,269
Grade 3 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		227,659
2020		379,975
2019		265,630
2018		199,222
2017		91,252
Prior		169,696
Revolving Loans		705,395
Revolving Loans Converted to Term Loans		917
Total loans		2,039,746
Grade 3 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2021		20,551
2020		36,543
2019		37,667
2018		22,455
2017		10,995
Prior		11,321
Revolving Loans		49,164
Total loans		188,696
Grade 4 [Member]
Financing Receivable Impaired [Line Items]
2021		53,039
2020		295,221
2019		295,377
2018		293,904
2017		242,637
Prior		478,097
Revolving Loans		182,864
Revolving Loans Converted to Term Loans		983
Total loans		1,842,122
Grade 4 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2021		5,365
2020		11,268
2019		3,883
2018		5,227
2017		2,869
Prior		20,396
Revolving Loans		10,055
Revolving Loans Converted to Term Loans		8
Total loans		59,071
Grade 4 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2021		3,127
2020		89,839
2019		91,719
2018		29,032
2017		8,761
Prior		9,294
Revolving Loans		11,335
Total loans		243,107
Grade 4 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2021		4,588
2020		11,960
2019		21,366
2018		25,480
2017		26,267
Prior		46,169
Revolving Loans		2,605
Total loans		138,435
Grade 4 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2021		32,617
2020		121,746
2019		120,200
2018		186,136
2017		194,686
Prior		384,973
Revolving Loans		7,710
Total loans		1,048,068
Grade 4 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		7,334
2020		54,622
2019		58,081
2018		47,689
2017		9,982
Prior		17,124
Revolving Loans		140,212
Revolving Loans Converted to Term Loans		975
Total loans		336,019
Grade 4 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2021		8
2020		5,786
2019		128
2018		340
2017		72
Prior		141
Revolving Loans		10,947
Total loans		17,422
Grade 5 [Member]
Financing Receivable Impaired [Line Items]
2021		2,658
2020		72,288
2019		35,922
2018		59,760
2017		27,266
Prior		146,137
Revolving Loans		13,033
Revolving Loans Converted to Term Loans		81
Total loans		357,145
Grade 5 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020		2,386
2019		568
2018		98
Revolving Loans		2,538
Total loans		5,590
Grade 5 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2021		2,625
2020		11,729
2019		491
2018		813
2017		76
Prior		112
Total loans		15,846
Grade 5 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020		315
2019		318
2018		154
2017		501
Prior		2,438
Revolving Loans		247
Total loans		3,973
Grade 5 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020		47,109
2019		15,471
2018		53,977
2017		25,264
Prior		143,502
Revolving Loans		2,305
Total loans		287,628
Grade 5 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		33
2020		10,735
2019		19,074
2018		4,655
2017		1,408
Prior		85
Revolving Loans		7,943
Revolving Loans Converted to Term Loans		81
Total loans		44,014
Grade 5 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020		14
2018		63
2017		17
Total loans		94
Grade 6 [Member]
Financing Receivable Impaired [Line Items]
2021		451
2020		27,987
2019		347
2018		1,467
2017		22,222
Prior		41,630
Revolving Loans		18,423
Total loans		112,527
Grade 6 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020		1,281
2019		42
2018		59
Prior		836
Total loans		2,218
Grade 6 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2020		4,442
Prior		1,192
Total loans		5,634
Grade 6 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020		21
2019		65
2018		2
2017		2
Prior		2,405
Total loans		2,495
Grade 6 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020		20,451
2019		166
2018		1,238
2017		22,159
Prior		33,684
Total loans		77,698
Grade 6 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		451
2020		1,792
2019		74
2018		168
2017		61
Prior		3,513
Revolving Loans		8,426
Total loans		14,485
Grade 6 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
Revolving Loans		9,997
Total loans		9,997
Grade 7 [Member]
Financing Receivable Impaired [Line Items]
2021		163
2020		1,136
2019		2,867
2018		11,807
2017		2,641
Prior		16,430
Revolving Loans		21,602
Total loans		56,646
Grade 7 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020		146
2019		61
2018		4
Prior		322
Total loans		533
Grade 7 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2020		397
2018		1,179
Prior		59
Total loans		1,635
Grade 7 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020		115
2019		989
2018		1,699
2017		2,483
Prior		5,532
Total loans		10,818
Grade 7 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020		16
2018		1,201
2017		14
Prior		9,335
Revolving Loans		1,439
Total loans		12,005
Grade 7 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2021		163
2020		462
2019		288
2018		7,710
2017		141
Prior		1,160
Revolving Loans		20,163
Total loans		30,087
Grade 7 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2019		1,529
2018		14
2017		3
Prior		22
Total loans		1,568
Grade 8 [Member]
Financing Receivable Impaired [Line Items]
Prior		43
Total loans		43
Grade 8 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
Prior		38
Total loans		38
Grade 8 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Prior		5
Total loans		$ 5
[1]	Includes $21.0 million and $46.8 million of residential mortgage loans held for sale at March 31, 2021 and December 31, 2020, respectively.

Loans and Allowance for Cred_13

Loans and Allowance for Credit Losses - Risk Grade by Category of Loan and Year of Origination/Renewal (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable Impaired [Line Items]
Loans held for sale	$ 20,991	$ 46,777
Residential Mortgage Loans [Member]
Financing Receivable Impaired [Line Items]
Loans held for sale	$ 20,991	$ 46,777

Loans and Allowance for Cred_14

Loans and Allowance for Credit Losses - Allowance for Credit Losses on Loans by Category of Loan (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Allowance for credit losses:
Allowance for credit losses, beginning balance	$ 316,068	$ 87,469
Charge-offs	(9,370)	(1,987)
Recoveries	512	1,186
Net charge-offs	(8,858)	(801)
Allowance for credit losses, ending balance	307,210	327,206
Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		240,538
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	7,824	2,971
Provision for credit losses	312
Charge-offs	(38)	(31)
Recoveries	5	32
Net charge-offs	(33)	1
Allowance for credit losses, ending balance	8,103	5,769
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		2,797
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	44,892	14,654
Provision for credit losses	5,221
Recoveries	5	12
Net charge-offs	5	12
Allowance for credit losses, ending balance	50,118	28,741
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		14,075
Real Estate [Member] | 1-4 Family [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	44,555	15,277
Provision for credit losses	3,194
Charge-offs	(54)	(29)
Recoveries	7	24
Net charge-offs	(47)	(5)
Allowance for credit losses, ending balance	47,702	23,539
Real Estate [Member] | 1-4 Family [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		8,267
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	87,857	12,332
Provision for credit losses	4,572
Charge-offs	(6,589)
Recoveries		81
Net charge-offs	(6,589)	81
Allowance for credit losses, ending balance	85,840	61,403
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		48,990
Commercial and Industrial [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	116,795	40,445
Provision for credit losses	(9,816)
Charge-offs	(1,754)	(611)
Recoveries	170	639
Net charge-offs	(1,584)	28
Allowance for credit losses, ending balance	105,395	180,097
Commercial and Industrial [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		139,624
Consumer and Other [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	14,145	1,790
Provision for credit losses	(3,483)
Charge-offs	(935)	(1,316)
Recoveries	325	398
Net charge-offs	(610)	(918)
Allowance for credit losses, ending balance	$ 10,052	27,657
Consumer and Other [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASU 2016-13		$ 26,785

Fair Value - Fair Value Assets

Fair Value - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available for sale securities:
Available for sale securities, at fair value	$ 638,355	$ 651,514
Fair Value, Measurements, Recurring [Member]
Available for sale securities:
Available for sale securities, at fair value	638,355	651,514
Fair Value, Measurements, Recurring [Member] | Loan Customer Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value	8,881	11,912
Fair Value, Measurements, Recurring [Member] | Financial Institution Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	8,881	11,912
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	638,355	651,514
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Loan Customer Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value	8,881	11,912
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Financial Institution Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	8,881	11,912
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations [Member]
Available for sale securities:
Available for sale securities, at fair value	601,419	612,334
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	601,419	612,334
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities [Member]
Available for sale securities:
Available for sale securities, at fair value	36,936	39,180
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	$ 36,936	$ 39,180

Fair Value - Additional Informa

Fair Value - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Fair Value Disclosures [Abstract]
Other real estate, additions	$ 281
Real estate owned outstanding	150
Additions to impaired loans	4,400
Impaired loans outstanding	$ 4,400

Fair Value - Summary of Carryin

Fair Value - Summary of Carrying and Fair Value Information of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets
Cash and due from banks	$ 1,947,235	$ 1,342,996
Federal funds sold	8,986	553
Held to maturity securities	9,529,602	8,039,142
Loans held for sale	20,991	46,777
Loans held for investment	17,345,506	17,357,788
Other real estate owned	462	10,593
Liabilities
Noninterest-bearing	9,820,445	9,151,233
Interest-bearing	18,942,660	18,209,259
Securities sold under repurchase agreements	377,106	389,583
Carrying Amount [Member]
Assets
Cash and due from banks	1,947,235	1,342,996
Federal funds sold	8,986	553
Held to maturity securities	9,449,647	7,891,306
Loans held for sale	20,991	46,777
Loans held for investment, net of allowance	17,038,296	17,041,720
Other real estate owned	462	10,593
Liabilities
Noninterest-bearing	9,820,445	9,151,233
Interest-bearing	18,942,660	18,209,259
Securities sold under repurchase agreements	377,106	389,583
Carrying Amount [Member] | Warehouse Purchase Program [Member]
Assets
Loans held for investment	2,272,389	2,842,379
Estimated Fair Value [Member]
Assets
Cash and due from banks	1,947,235	1,342,996
Federal funds sold	8,986	553
Held to maturity securities	9,529,602	8,039,142
Loans held for sale	20,991	46,777
Loans held for investment, net of allowance	17,137,592	17,118,745
Other real estate owned	462	10,593
Liabilities
Noninterest-bearing	9,820,445	9,151,233
Interest-bearing	18,954,529	18,227,623
Securities sold under repurchase agreements	377,115	389,595
Estimated Fair Value [Member] | Level 1 [Member]
Assets
Cash and due from banks	1,947,235	1,342,996
Federal funds sold	8,986	553
Estimated Fair Value [Member] | Level 2 [Member]
Assets
Held to maturity securities	9,529,602	8,039,142
Loans held for sale	20,991	46,777
Other real estate owned	462	10,593
Liabilities
Noninterest-bearing	9,820,445	9,151,233
Interest-bearing	18,954,529	18,227,623
Securities sold under repurchase agreements	377,115	389,595
Estimated Fair Value [Member] | Level 3 [Member]
Assets
Loans held for investment, net of allowance	17,137,592	17,118,745
Estimated Fair Value [Member] | Warehouse Purchase Program [Member]
Assets
Loans held for investment	2,272,389	2,842,379
Estimated Fair Value [Member] | Warehouse Purchase Program [Member] | Level 2 [Member]
Assets
Loans held for investment	$ 2,272,389	$ 2,842,379

Goodwill and Core Deposit Int_3

Goodwill and Core Deposit Intangibles - Goodwill and Core Deposit Intangibles (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill, Beginning balance		$ 3,231,636	$ 3,223,671	$ 3,223,671
Goodwill, Measurement period adjustment of LegacyTexas Merger	[1]			7,965
Goodwill, Ending balance		3,231,636		3,231,636
Core Deposit Intangibles, Beginning balance		73,235	86,404	86,404
Core Deposit Intangibles, Amortization		(2,931)	$ (3,363)	(13,169)
Core Deposit Intangibles, Ending balance		$ 70,304		$ 73,235
[1]	LegacyTexas Financial Group, Inc. (“LegacyTexas”) merged into Bancshares on November 1, 2019.

Goodwill and Core Deposit Int_4

Goodwill and Core Deposit Intangibles - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Schedule Of Intangible Assets And Goodwill [Line Items]
Impairment recorded on goodwill and core deposit intangibles	$ 0
Amortization expense related to intangible assets	$ 2,931,000	$ 3,363,000	$ 13,169,000
Minimum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Finite-lived intangible assets, useful life	10 years
Maximum [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Finite-lived intangible assets, useful life	15 years

Goodwill and Core Deposit Int_5

Goodwill and Core Deposit Intangibles - Estimated Aggregate Future Amortization Expense for Core Deposit Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Remaining 2021	$ 8,621
2022	10,336
2023	9,360
2024	8,699
2025	8,173
Thereafter	25,115
Total	$ 70,304	$ 73,235	$ 86,404

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)Planshares	Mar. 31, 2020USD ($)shares	Dec. 31, 2012shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock-based employee compensation plans | Plan	2
Total unrecognized compensation expense related to stock-based compensation arrangements | $	$ 29.3
Weighted-average period of cost expected to be recognized	1 year 11 months 19 days
Number of shares outstanding	0	0
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense | $	$ 3.4	$ 3.3
2020 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares authorized for issuance	2,500,000
Number of restricted shares granted	391,155
Share issued	4,576
2012 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares authorized for issuance			1,250,000
Number of restricted shares granted	149,987
Share issued	696,388

Contractual Obligations and O_3

Contractual Obligations and Off-Balance Sheet Items - Additional Information (Details)	3 Months Ended
	Mar. 31, 2021USD ($)SubleaseArrangement	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Contractual Obligations And Off Balance Sheet Items [Line Items]
Operating lease, right-of-use asset	$ 54,700,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsMember
Operating lease, liability	$ 54,700,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesMember
Number of sublease arrangement | SubleaseArrangement	1
Sublease income	$ 450,000	$ 0
Operating lease, weighted average remaining lease term	6 years 10 months 24 days
Operating lease, weighted average discount rate, percent	2.26%
Operating lease, payments	$ 3,500,000	$ 3,600,000
Right-of-Use asset obtained in exchange for operating lease liability	258,000
Allowance for credit losses on off-balance sheet credit exposures	$ 29,947,000		$ 29,947,000
Minimum [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
Lessee operating lease remaining lease term	1 year
Maximum [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
Lessee operating lease remaining lease term	18 years

Contractual Obligations and O_4

Contractual Obligations and Off-Balance Sheet Items - Future Undiscounted Cash Payments Associated with its Operating Leases (Details) $ in Thousands	Mar. 31, 2021USD ($)
Leases [Abstract]
Remaining 2021	$ 8,305
2022	10,608
2023	9,860
2024	8,938
2025	8,546
2026	7,853
Thereafter	12,716
Total undiscounted lease payments	$ 66,826

Contractual Obligations and O_5

Contractual Obligations and Off-Balance Sheet Items - Summary of Commitments Associated with Outstanding Standby Letters of Credit and Commitments to Extend Credit (Details) - Guarantee Obligations [Member] $ in Thousands	Mar. 31, 2021USD ($)
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	$ 3,310,626
More than 1 year but less than 3 years	785,966
3 years or more but less than 5 years	370,683
5 years or more	1,127,890
Total	5,595,165
Unused capacity on Warehouse Purchase Program loans [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	1,500,611
Total	1,500,611
Commitments to Extend Credit [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	1,713,071
More than 1 year but less than 3 years	779,833
3 years or more but less than 5 years	369,880
5 years or more	1,127,890
Total	3,990,674
Standby Letters of Credit [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	96,944
More than 1 year but less than 3 years	6,133
3 years or more but less than 5 years	803
5 years or more	0
Total	$ 103,880

Other Comprehensive Income - Ta

Other Comprehensive Income - Tax Effects Allocated to Each Component of Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Equity [Abstract]
Change in unrealized gain (loss) during period, before tax amount	$ (4)	$ (4,183)
Change in unrealized gain (loss) during period, tax effect	1	878
Change in unrealized gain (loss) during period, net of tax amount	(3)	(3,305)
Total securities available for sale, before tax amount	(4)	(4,183)
Total securities available for sale, tax effect	1	878
Total securities available for sale, net of tax amount	(3)	(3,305)
Total other comprehensive income (loss), before tax amount	(4)	(4,183)
Total other comprehensive income (loss), tax effect	1	878
Other comprehensive loss, net of tax	$ (3)	$ (3,305)

Other Comprehensive Income - Ac

Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income Associated with Securities Available for Sale, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Beginning balance, accumulated other comprehensive income	$ 769	$ 602
Other comprehensive loss	(3)	(3,305)
Ending balance, accumulated other comprehensive income	766	(2,703)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance, accumulated other comprehensive income	769	602
Other comprehensive loss	(3)	(3,305)
Ending balance, accumulated other comprehensive income	$ 766	$ (2,703)

Derivative Financial Instrume_3

Derivative Financial Instruments - Schedule of Notional Balances and Fair Value of Derivative Positions (Details) - Commercial Loan Interest Rate Swaps and Caps [Member] - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Loan Customer Counterparty [Member]
Derivatives Fair Value [Line Items]
Outstanding Notional Balance	$ 249,433	$ 224,684
Derivative financial instruments, assets at fair value	8,881	11,912
Financial Institution Counterparty [Member]
Derivatives Fair Value [Line Items]
Outstanding Notional Balance	249,433	224,684
Derivative financial instruments, liabilities at fair value	$ 8,881	$ 11,912

Derivative Financial Instrume_4

Derivative Financial Instruments - Schedule of Weighted Average Received and Paid Interest Rates for Interest Rate Swaps Outstanding (Details) - Commercial Loan Interest Rate Swaps and Caps [Member] - Loan Customer Counterparty [Member]	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Weighted-Average Interest Rate Received	0.0262	0.0283
Weighted-Average Interest Rate Paid	0.0068	0.0079

Derivative Financial Instrume_5

Derivative Financial Instruments - Additional Information (Details) - Interest Rate Swap - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Credit exposure	$ 8,900,000	$ 11,900,000
Cash collateral pledged	10,300,000	$ 13,800,000
Financial Institution Counterparty [Member]
Derivative [Line Items]
Credit exposure	$ 0

Derivative Financial Instrume_6

Derivative Financial Instruments - Schedule of Income (Loss) from Derivatives (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Interest Rate Lock Commitments [Member]
Derivative Instruments Gain Loss [Line Items]
Derivatives not designated as hedging instruments	$ 1,112
Forward Mortgage-Backed Securities Trades [Member]
Derivative Instruments Gain Loss [Line Items]
Derivatives not designated as hedging instruments	$ (1,937)