Prosperity Bancshares (PB) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
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, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding (in shares)		92,660,712
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, 2020	Dec. 31, 2019
ASSETS
Cash and due from banks	$ 381,458	$ 573,589
Federal funds sold	676	519
Total cash and cash equivalents	382,134	574,108
Available for sale securities, at fair value	315,255	287,663
Held to maturity securities, at cost (fair value of $8,136,374 and $8,303,851, respectively)	7,980,240	8,282,393
Total securities	8,295,495	8,570,056
Loans held for sale	65,035	80,959
Loans held for investment	17,348,398	17,211,625
Total loans	19,127,195	18,845,346
Less: allowance for credit losses on loans	(327,206)	(87,469)
Loans, net	18,799,989	18,757,877
Accrued interest receivable	76,038	80,797
Goodwill	3,223,144	3,223,671
Core deposit intangibles, net	83,041	86,404
Bank premises and equipment, net	327,293	326,832
Other real estate owned	5,452	6,936
Bank owned life insurance (BOLI)	323,338	321,793
Federal Home Loan Bank of Dallas stock	66,213	83,945
Other assets	161,362	153,289
TOTAL ASSETS	31,743,499	32,185,708
Deposits:
Noninterest-bearing	7,461,323	7,763,894
Interest-bearing	16,365,034	16,435,838
Total deposits	23,826,357	24,199,732
Fed funds purchased and other borrowings	1,338,429	1,303,730
Securities sold under repurchase agreements	344,695	377,294
Subordinated notes	125,585	125,804
Accrued interest payable	8,730	8,585
Allowance for credit losses on off-balance sheet credit exposure	29,947	5,599
Other liabilities	214,182	194,129
Total liabilities	25,887,925	26,214,873
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; 92,651,712 shares issued and outstanding at March 31, 2020; 94,746,019 shares issued and outstanding at December 31, 2019	92,651	94,746
Capital surplus	3,629,893	3,734,519
Retained earnings	2,135,733	2,140,968
Accumulated other comprehensive (loss) income —net unrealized (loss) gain on available for sale securities, net of tax (benefit) expense of $(718) and $160, respectively	(2,703)	602
Total shareholders’ equity	5,855,574	5,970,835
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	31,743,499	32,185,708
Warehouse Purchase Program [Member]
ASSETS
Loans held for investment	1,713,762	1,552,762
Total loans	$ 1,713,762	$ 1,552,762

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Held to maturity securities, fair value	$ 8,136,374	$ 8,303,851
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)	92,651,712	94,746,019
Common stock, shares outstanding (in shares)	92,651,712	94,746,019
Accumulated other comprehensive income net unrealized (loss) gain on available for sale securities, tax (benefit) expense	$ (718)	$ 160

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
INTEREST INCOME:
Loans, including fees	$ 247,243	$ 130,065
Securities	48,282	55,648
Federal funds sold and other earning assets	713	402
Total interest income	296,238	186,115
INTEREST EXPENSE:
Deposits	35,018	25,128
Other borrowings	2,932	5,317
Securities sold under repurchase agreements	757	759
Subordinated notes	1,500
Total interest expense	40,207	31,204
NET INTEREST INCOME	256,031	154,911
PROVISION FOR CREDIT LOSSES		700
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	256,031	154,211
NONINTEREST INCOME:
Nonsufficient funds (NSF) fees	9,443	7,816
Credit card, debit card and ATM card income	7,474	5,971
Service charges on deposit accounts	6,104	4,998
Trust income	2,662	2,595
Mortgage income	2,010	722
Brokerage income	650	673
Net (loss) gain on sale of assets	(385)	58
Other	6,430	5,311
Total noninterest income	34,388	28,144
NONINTEREST EXPENSE:
Salaries and employee benefits	77,282	51,073
Net occupancy and equipment	8,980	5,466
Credit and debit card, data processing and software amortization	11,421	4,573
Regulatory assessments and FDIC insurance	2,078	2,374
Core deposit intangibles amortization	3,363	1,319
Depreciation	4,768	3,104
Communications	3,195	2,270
Other real estate expense, net	(84)	(94)
Merger related expenses	544
Other	13,194	8,486
Total noninterest expense	124,741	78,571
INCOME BEFORE INCOME TAXES	165,678	103,784
PROVISION FOR INCOME TAXES	34,830	21,382
NET INCOME	$ 130,848	$ 82,402
EARNINGS PER SHARE:
Basic	$ 1.39	$ 1.18
Diluted	$ 1.39	$ 1.18

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 130,848	$ 82,402
Securities available for sale:
Change in unrealized (losses) gains during the period	(4,183)	503
Total other comprehensive (loss) income	(4,183)	503
Deferred tax benefit (expense) related to other comprehensive (loss) income	878	(106)
Other comprehensive (loss) income, net of tax	(3,305)	397
Comprehensive income	$ 127,543	$ 82,799

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
BALANCE at Dec. 31, 2018		$ 4,052,824	$ 69,847	$ 2,045,351	$ 1,937,316	$ 310
BALANCE (in shares) at Dec. 31, 2018			69,846,825
Net income		82,402			82,402
Other comprehensive income (loss)		397				397
Common stock issued in connection with the issuance of restricted stock awards, net			$ (1)	1
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)			(900)
Stock based compensation expense		2,804		2,804
Cash dividends declared		(28,637)			(28,637)
BALANCE at Mar. 31, 2019		4,109,790	$ 69,846	2,048,156	1,991,081	707
BALANCE (in shares) at Mar. 31, 2019			69,845,925
BALANCE at Dec. 31, 2019		5,970,835	$ 94,746	3,734,519	2,140,968	602
BALANCE (in shares) at Dec. 31, 2019			94,746,019
Cumulative change in accounting principle upon adoption of ASU 2016-13 and other at Dec. 31, 2019	[1]	(92,860)			(92,860)
BALANCE AT JANUARY 1, 2020 (AS ADJUSTED FOR CHANGE IN ACCOUNTING STANDARD) at Dec. 31, 2019		5,877,975	$ 94,746	3,734,519	2,048,108	602
Net income		130,848			130,848
Other comprehensive income (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
[1]	(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, 2020	Mar. 31, 2019
Retained Earnings [Member]
Cash dividend declared, per share (in dollars per share)	$ 0.46	$ 0.41

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 130,848	$ 82,402
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and core deposit intangibles amortization	8,131	4,423
Provision for credit losses		700
Net amortization of premium on investments	8,005	6,589
Net gain on sale of other real estate and repossessed assets	(130)	(177)
Net loss (gain) on sale or write down of premises and equipment	385	(58)
Net accretion of discount on loans	(28,482)	(1,793)
Net amortization of premium on deposits	(2,270)
Gain on sale of loans	(1,360)	(711)
Proceeds from sale of loans held for sale	96,119	39,556
Originations of loans held for sale	(79,377)	(33,876)
Stock based compensation expense	3,340	2,804
Decrease in accrued interest receivable and other assets	41,497	7,034
Increase in accrued interest payable and other liabilities	33,225	26,672
Net cash provided by operating activities	209,931	133,565
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities and principal paydowns of held to maturity securities	500,666	391,109
Purchase of held to maturity securities	(206,563)	(130,760)
Proceeds from maturities and principal paydowns of available for sale securities	4,011,040	3,004,707
Purchase of available for sale securities	(4,042,771)	(2,999,821)
Originations of WPP loans	(6,196,020)
Proceeds from pay-offs of WPP	6,035,020
Net decrease (increase) in loans held for investment	23,161	(49,963)
Purchase of bank premises and equipment	(6,329)	(3,633)
Proceeds from sale of bank premises, equipment and other real estate	2,180	1,347
Proceeds from insurance claims		2,132
Net cash provided by investing activities	120,384	215,118
CASH FLOWS FROM FINANCING ACTIVITIES:
Net (decrease) increase in noninterest-bearing deposits	(302,571)	7,592
Net decrease in interest-bearing deposits	(68,534)	(66,380)
Net proceeds from (repayments of) other short-term borrowings	35,000	(350,000)
Repayments of other long-term borrowings	(301)	(174)
Net decrease in securities sold under repurchase agreements	(32,599)	(30,147)
Repurchase of common stock	(110,061)
Payments of cash dividends	(43,223)	(28,637)
Net cash used in financing activities	(522,289)	(467,746)
NET DECREASE IN CASH AND CASH EQUIVALENTS	(191,974)	(119,063)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	574,108	411,127
CASH AND CASH EQUIVALENTS, END OF PERIOD	382,134	292,064
NONCASH ACTIVITIES:
Acquisition of real estate through foreclosure of collateral	112	1,370
SUPPLEMENTAL INFORMATION:
Interest paid	$ 40,062	$ 30,980

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2020
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, 2019. Operating results for the three-month period ended March 31, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020 or any other period.

Income Per Common Share

Income Per Common Share	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 Amount Per Share Amount Amount Per Share Amount (Amounts in thousands, except per share data) Net income $ 130,848 $ 82,402 Basic: Weighted average shares outstanding 94,371 $ 1.39 69,847 $ 1.18 Diluted: Weighted average shares outstanding 94,371 $ 1.39 69,847 $ 1.18 As of March 31, 2020, 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, 2020 or 2019 that would have had an anti-dilutive effect on the above computation.

New Accounting Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2020
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 (ii) 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 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. ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments (“ASC 326”).” On January 1, 2020 the Company adopted ASU 2016-13 which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (“CECL”) methodology. CECL requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of CECL is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. The Company adopted ASU 2016-13 using the modified-retrospective method for all financial assets measured at amortized cost and off-balance sheet credit exposures. Reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior periods are reported with previously applicable GAAP. Upon adoption of ASU 2016-13, the Company recognized an increase in allowance for credit losses for loans of $108.7 million, of which $102.5 million was related to LegacyTexas Financial Group, Inc. (“LegacyTexas”), which merged into Bancshares on November 1, 2019, and an increase in allowance for credit losses for off-balance sheet credit exposures of $24.4 million, of which $6.3 million was related to LegacyTexas, with a corresponding decrease in retained earnings (pre-tax). Additionally, the Company adopted ASU 2016-13 using the prospective transition approach for financial assets purchased with credit deterioration. The Company recognized an increase in the allowance for credit losses for loans of $131.8 million, of which $130.3 million was related to LegacyTexas, due to the reclass of purchased credit deteriorated discounts as the result of adopting ASU 2016-13. See Note 5 “Loans and Allowance for Credit Losses” for additional information. The Company recognized no allowance for credit losses related to debt securities. See Note 4 “Securities” for additional information. The following table illustrates the impact of adopting ASU 2016-13: January 1, 2020 As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption (Dollars in thousands) Assets: Loans Construction, land development and other land loans $ 28,729 $ 14,654 $ 14,075 Agriculture and agriculture real estate (includes farmland) 5,768 2,971 2,797 1-4 family (includes home equity) 23,544 15,277 8,267 Commercial real estate (includes multi-family residential) 61,322 12,332 48,990 Commercial and industrial 180,069 40,445 139,624 Consumer and other 28,575 1,790 26,785 Allowance for credit losses on loans $ 328,007 $ 87,469 $ 240,538 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 29,947 $ 5,599 $ 24,348

Securities

Securities	3 Months Ended
	Mar. 31, 2020
Investments Debt And Equity Securities [Abstract]
Securities	4. SECURITIES The amortized cost and fair value of investment securities were as follows: March 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 305 $ 1 $ — $ 306 Collateralized mortgage obligations 269,777 175 (3,485 ) 266,467 Mortgage-backed securities 48,594 639 (751 ) 48,482 Total $ 318,676 $ 815 $ (4,236 ) $ 315,255 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 6,959 $ 76 $ — $ 7,035 States and political subdivisions 208,744 7,172 (563 ) 215,353 Collateralized mortgage obligations 184,540 4,156 (39 ) 188,657 Mortgage-backed securities 7,579,997 146,864 (1,532 ) 7,725,329 Total $ 7,980,240 $ 158,268 $ (2,134 ) $ 8,136,374 December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 470 $ 1 $ — $ 471 Collateralized mortgage obligations 235,222 690 (139 ) 235,773 Mortgage-backed securities 51,209 659 (449 ) 51,419 Total $ 286,901 $ 1,350 $ (588 ) $ 287,663 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 13,933 $ 58 $ — $ 13,991 States and political subdivisions 238,347 7,632 (189 ) 245,790 Collateralized mortgage obligations 203,470 1,115 (373 ) 204,212 Mortgage-backed securities 7,826,643 48,060 (34,845 ) 7,839,858 Total $ 8,282,393 $ 56,865 $ (35,407 ) $ 8,303,851 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. Furthermore, as of March 31, 2020 , 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, 2020 , 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 are 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, 2020, the Company’s municipal securities represent 2.5% 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, 2020, 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, 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 $ 145,162 $ (3,473 ) $ 1,725 $ (12 ) $ 146,887 $ (3,485 ) Mortgage-backed securities 32,690 (751 ) 7 — 32,697 (751 ) Total $ 177,852 $ (4,224 ) $ 1,732 $ (12 ) $ 179,584 $ (4,236 ) Held to Maturity States and political subdivisions $ 52,617 $ (563 ) $ — $ — $ 52,617 $ (563 ) Collateralized mortgage obligations 9,426 (39 ) — — 9,426 (39 ) Mortgage-backed securities 41,092 (525 ) 210,809 (1,007 ) 251,901 (1,532 ) Total $ 103,135 $ (1,127 ) $ 210,809 $ (1,007 ) $ 313,944 $ (2,134 ) December 31, 2019 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 $ 50,245 $ (136 ) $ 1,818 $ (3 ) $ 52,063 $ (139 ) Mortgage-backed securities 34,901 (449 ) 10 — 34,911 (449 ) Total $ 85,146 $ (585 ) $ 1,828 $ (3 ) $ 86,974 $ (588 ) Held to Maturity States and political subdivisions $ 58,329 $ (183 ) $ 3,241 $ (6 ) $ 61,570 $ (189 ) Collateralized mortgage obligations 54,890 (373 ) — — 54,890 (373 ) Mortgage-backed securities 947,314 (3,017 ) 3,110,765 (31,828 ) 4,058,079 (34,845 ) Total $ 1,060,533 $ (3,573 ) $ 3,114,006 $ (31,834 ) $ 4,174,539 $ (35,407 ) At March 31, 2020 and December 31, 2019, there were 35 securities and 138 securities, respectively, in an unrealized loss position for 12 months or more. The amortized cost and fair value of investment securities at March 31, 2020, 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 $ 31,833 $ 31,993 $ 305 $ 306 Due after one year through five years 119,381 123,392 — — Due after five years through ten years 57,735 60,219 — — Due after ten years 6,754 6,784 — — Subtotal 215,703 222,388 305 306 Mortgage-backed securities and collateralized mortgage obligations 7,764,537 7,913,986 318,371 314,949 Total $ 7,980,240 $ 8,136,374 $ 318,676 $ 315,255 The Company recorded no gain or loss on the sale of securities for the three months ended March 31, 2020 and 2019. As of March 31, 2020, the Company did not own any non-agency collateralized mortgage obligations. At March 31, 2020 and December 31, 2019, 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 $5.67 billion and $5.98 billion and a fair value of $5.78 billion and $5.99 billion at March 31, 2020 and December 31, 2019, 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, 2020
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, 2020 December 31, 2019 (Dollars in thousands) Residential mortgage loans held for sale $ 65,035 $ 80,959 Commercial and industrial 3,218,763 3,205,595 Real estate: Construction, land development and other land loans 2,051,021 2,064,167 1-4 family residential (includes home equity) 4,444,106 4,306,452 Commercial real estate (includes multi-family residential) 6,576,213 6,556,285 Farmland 467,372 495,558 Agriculture 167,923 185,297 Consumer and other 423,000 398,271 Total loans held for investment, excluding Warehouse Purchase Program 17,348,398 17,211,625 Warehouse Purchase Program 1,713,762 1,552,762 Total loans, including Warehouse Purchase Program $ 19,127,195 $ 18,845,346 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 68.3% of the Company’s total loan portfolio at March 31, 2020. As of March 31, 2020 and December 31, 2019, there were no concentrations of loans related to any single industry in excess of 10% Related Party Loans. As of March 31, 2020 and December 31, 2019, loans outstanding to directors, officers and their affiliates totaled $4.1 million and $4.2 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, 2020 As of and for the year ended December (Dollars in thousands) Beginning balance on January 1 $ 4,152 $ 1,923 New loans — 1 Transfers — 2,500 Repayments (79 ) (272 ) Ending balance $ 4,073 $ 4,152 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. 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 writedowns 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, 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 $ 70,850 $ — $ 70,850 $ 1,125 $ 1,979,046 $ 2,051,021 Warehouse Purchase Program loans — — — — 1,713,762 1,713,762 Agriculture and agriculture real estate (includes farmland) 3,017 868 3,885 28 631,382 635,295 1-4 family (includes home equity) (1) 39,525 2,213 41,738 26,632 4,440,771 4,509,141 Commercial real estate (includes multi-family residential) 15,284 169 15,453 14,685 6,546,075 6,576,213 Commercial and industrial 7,653 2 7,655 15,720 3,195,388 3,218,763 Consumer and other 11,059 3 11,062 4 411,934 423,000 Total $ 147,388 $ 3,255 $ 150,643 $ 58,194 $ 18,918,358 $ 19,127,195 December 31, 2019 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 $ 16,470 $ — $ 16,470 $ 1,142 $ 2,046,555 $ 2,064,167 Warehouse Purchase Program loans — — — — 1,552,762 1,552,762 Agriculture and agriculture real estate (includes farmland) 466 — 466 103 680,286 680,855 1-4 family (includes home equity) (1) 43,884 441 44,325 24,413 4,318,673 4,387,411 Commercial real estate (includes multi-family residential) 10,669 — 10,669 12,714 6,532,902 6,556,285 Commercial and industrial 7,249 — 7,249 16,809 3,181,537 3,205,595 Consumer and other 1,708 — 1,708 62 396,501 398,271 Total $ 80,446 $ 441 $ 80,887 $ 55,243 $ 18,709,216 $ 18,845,346 (1) Includes $65.0 million and $81.0 million of residential mortgage loans held for sale at March 31, 2020 and December 31, 2019, respectively. The following table presents information regarding nonperforming assets as of the dates indicated: March 31, 2020 December 31, 2019 (Dollars in thousands) Nonaccrual loans (1) (2) $ 58,194 $ 55,243 Accruing loans 90 or more days past due 3,255 441 Total nonperforming loans 61,449 55,684 Repossessed assets 278 323 Other real estate 5,452 6,936 Total nonperforming assets $ 67,179 $ 62,943 Nonperforming assets to total loans and other real estate 0.35 % 0.33 % Nonperforming assets to total loans, excluding Warehouse Purchase Program loans, and other real estate 0.39 % 0.36 % (1) Includes troubled debt restructurings of $13.0 million and $13.6 million as of March 31, 2020 and December 31, 2019, 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 $67.2 million in nonperforming assets at March 31, 2020 compared with $62.9 million at December 31, 2019. Nonperforming assets were 0.35% of total loans and other real estate at March 31, 2020 compared with 0.33% of total loans and other real estate at December 31, 2019. If interest on nonaccrual loans had been accrued under the original loan terms, approximately $869 thousand and $602 thousand would have been recorded as income for the three months ended March 31, 2020 and 2019, respectively. The Company had $58.2 million in nonaccrual loans at March 31, 2020 compared with $37.5 million at March 31, 2019. 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 since origination. 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 yield 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, 2020 and December 31, 2019 . March 31, 2020 December 31, 2019 (Dollars in thousands) PCD loans: Outstanding balance $ 355,160 $ 410,785 Discount (1) (29,460 ) (167,320 ) (2) Recorded investment $ 325,700 $ 243,465 (1) ASU 2016-13 became effective for the Company on January 1, 2020. (2) Includes $131.8 million in PCD loans credit discount. Changes in the accretable yield for acquired PCD loans for the three months ended March 31, 2020 and 2019 were as follows: Three Months Ended March 31, 2020 2019 (Dollars in thousands) Balance at beginning of period $ 35,654 $ 1,534 Adjustments (175 ) 19 Accretion (6,019 ) (319 ) Balance at March 31, $ 29,460 $ 1,234 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 adoption of ASU 2016-13, “ Financial Instruments-Credit-Losses (ASC Topic 326) – Measurement of Credit Losses on Financial Instruments 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, 2020 and December 31, 2019. March 31, 2020 December 31, 2019 (Dollars in thousands) Non-PCD loans: Outstanding balance $ 5,744,368 $ 6,102,540 Discount (87,613 ) (110,130 ) Recorded investment $ 5,656,755 $ 5,992,410 Changes in the discount accretion for Non-PCD loans for the three months ended March 31, 2020 and 2019 were as follows: Three Months Ended March 31, 2020 2019 (Dollars in thousands) Balance at beginning of period $ 110,130 $ 14,833 Accretion charge-offs (54 ) — Accretion (22,463 ) (1,474 ) Balance at March 31, $ 87,613 $ 13,359 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 is 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 table presents loans by risk grade and category of loan at March 31, 2020. Impaired loans include loans in risk grades 7, 8 and 9, as well as any PCD loan that has deteriorated since the acquisition date. Term Loans Amortized Cost Basis by Origination Year 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Construction, Land Development and Other Land Loans Grade 1 $ — $ — $ — $ — $ — $ 29 $ — $ — $ 29 Grade 2 — 1,119 — 90 135 362 — — 1,706 Grade 3 215,615 818,291 437,168 125,916 28,173 64,486 132,231 624 1,822,504 Grade 4 3,829 28,601 31,715 122,176 3,763 9,340 12,566 — 211,990 Grade 5 — — 2,564 — — 363 — — 2,927 Grade 6 — — — — 602 1,688 — — 2,290 Grade 7 — — — — — 390 734 — 1,124 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — 7,875 129 447 — — — — 8,451 Total $ 219,444 $ 855,886 $ 471,576 $ 248,629 $ 32,673 $ 76,658 $ 145,531 $ 624 $ 2,051,021 Agriculture and Agriculture Real Estate (includes Farmland) Grade 1 $ 167 $ 2,099 $ 298 $ 258 $ — $ 1 $ 9,019 $ — $ 11,842 Grade 2 — — 13 358 8 1,756 — — 2,135 Grade 3 26,553 100,074 78,662 62,508 59,832 126,263 82,030 4 535,926 Grade 4 5,561 10,223 4,704 2,555 6,860 23,985 17,707 1,158 72,753 Grade 5 637 4,190 329 — — 990 2,929 — 9,075 Grade 6 1,331 — — — 186 188 — — 1,705 Grade 7 — — 28 — — — — — 28 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 978 223 — — — 312 318 — 1,831 Total $ 35,227 $ 116,809 $ 84,034 $ 65,679 $ 66,886 $ 153,495 $ 112,003 $ 1,162 $ 635,295 1-4 Family (includes Home Equity) (1) Grade 1 $ 100 $ — $ — $ — $ — $ — $ 204 $ — $ 304 Grade 2 292 775 1,018 895 265 9,918 1,136 — 14,299 Grade 3 255,393 1,011,615 715,736 589,506 556,826 1,097,425 146,389 1,470 4,374,360 Grade 4 724 14,698 7,402 12,131 10,200 33,866 1,636 521 81,178 Grade 5 — 224 2,052 1,282 111 2,112 — — 5,781 Grade 6 — 29 — 333 138 1,948 24 — 2,472 Grade 7 — 1,787 1,173 2,501 1,159 13,834 3,509 — 23,963 Grade 8 — — — — 10 93 — — 103 Grade 9 — — — — — — — — — PCD Loans — — — — 264 5,366 1,051 — 6,681 Total $ 256,509 $ 1,029,128 $ 727,381 $ 606,648 $ 568,973 $ 1,164,562 $ 153,949 $ 1,991 $ 4,509,141 Term Loans Amortized Cost Basis by Origination Year 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Commercial Real Estate (includes Multi-Family Residential) Grade 1 $ — $ — $ — $ — $ — $ 1,385 $ — $ — $ 1,385 Grade 2 5,862 935 — 7,948 209 4,986 — — 19,940 Grade 3 127,368 1,161,018 1,183,252 1,106,578 653,077 1,362,652 120,075 — 5,714,020 Grade 4 9,140 34,890 67,523 129,964 164,600 246,546 17,749 — 670,412 Grade 5 — — 2,259 12,909 4,251 14,463 — — 33,882 Grade 6 — 3,745 1,250 196 3,239 11,153 1,500 — 21,083 Grade 7 — 6 — 17 14,412 224 — — 14,659 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 27,593 21,709 5,476 27,168 578 18,308 — — 100,832 Total $ 169,963 $ 1,222,303 $ 1,259,760 $ 1,284,780 $ 840,366 $ 1,659,717 $ 139,324 $ — $ 6,576,213 Commercial and Industrial Grade 1 $ 9,544 $ 19,031 $ 5,023 $ 1,221 $ 921 $ 46,114 $ 22,818 $ 35 $ 104,707 Grade 2 341 221 1,280 1,697 1,497 1,534 85,570 — 92,140 Grade 3 66,617 428,024 246,098 125,966 97,689 164,771 1,337,870 518 2,467,553 Grade 4 17,653 56,789 24,562 24,629 11,193 32,869 132,853 483 301,031 Grade 5 2,087 18,781 840 241 376 21 4,298 — 26,644 Grade 6 25 581 2,828 — 122 2,509 27,007 — 33,072 Grade 7 — 758 12,577 872 929 284 99 — 15,519 Grade 8 — — — — 13 — — — 13 Grade 9 — — — — — — — — — PCD Loans 996 22,175 9,685 11,769 3,750 1,140 128,569 — 178,084 Total $ 97,263 $ 546,360 $ 302,893 $ 166,395 $ 116,490 $ 249,242 $ 1,739,084 $ 1,036 $ 3,218,763 Consumer and Other Grade 1 $ 6,476 $ 20,300 $ 6,398 $ 3,273 $ 1,913 $ 1,192 $ 1,393 $ — $ 40,945 Grade 2 1,707 10,878 1,011 41,282 1,676 — 1,467 — 58,021 Grade 3 13,862 80,824 39,194 27,396 9,741 19,122 72,968 147 263,254 Grade 4 1,293 4,925 31 5 120 174 21,057 — 27,605 Grade 5 — — 72 18 — — 1,717 — 1,807 Grade 6 — 1,534 — — — — 1 — 1,535 Grade 7 — 1 7 — — 1 3 — 12 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 4,385 8,947 — — — — 16,489 — 29,821 Total $ 27,723 $ 127,409 $ 46,713 $ 71,974 $ 13,450 $ 20,489 $ 115,095 $ 147 $ 423,000 Term Loans Amortized Cost Basis by Origination Year 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Warehouse Purchase Program Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 — — — — — — — — — Grade 3 1,713,762 — — — — — — — 1,713,762 Grade 4 — — — — — — — — — Grade 5 — — — — — — — — — Grade 6 — — — — — — — — — Grade 7 — — — — — — — — — Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — — — — — — — — — Total $ 1,713,762 $ — $ — $ — $ — $ — $ — $ — $ 1,713,762 Total Grade 1 $ 16,287 $ 41,430 $ 11,719 $ 4,752 $ 2,834 $ 48,721 $ 33,434 $ 35 $ 159,212 Grade 2 8,202 13,928 3,322 52,270 3,790 18,556 88,173 — 188,241 Grade 3 2,419,170 3,599,846 2,700,110 2,037,870 1,405,338 2,834,719 1,891,563 2,763 16,891,379 Grade 4 38,200 150,126 135,937 291,460 196,736 346,780 203,568 2,162 1,364,969 Grade 5 2,724 23,195 8,116 14,450 4,738 17,949 8,944 — 80,116 Grade 6 1,356 5,889 4,078 529 4,287 17,486 28,532 — 62,157 Grade 7 — 2,552 13,785 3,390 16,500 14,733 4,345 — 55,305 Grade 8 — — — — 23 93 — — 116 Grade 9 — — — — — — — — — PCD Loans 33,952 60,929 15,290 39,384 4,592 25,126 146,427 — 325,700 Total $ 2,519,891 $ 3,897,895 $ 2,892,357 $ 2,444,105 $ 1,638,838 $ 3,324,163 $ 2,404,986 $ 4,960 $ 19,127,195 (1) Includes $65.0 million of residential mortgage loans held for sale at March 31, 2020. Allowance for Credit Losses on Loans. The allowance for credit losses is established 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, 2020 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 and (3) provisions for credit losses charged to earnings that increase 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 loan loss experience, general 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, 2020 and 2019. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. 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 Beginning balance, prior to adoption of ASC 326 $ 14,654 $ 2,971 $ 15,277 $ 12,332 $ 40,445 $ 1,790 $ 87,469 Impact of adoption ASC 326 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 Three Months Ended Balance December 31, 2018 $ 15,582 $ 3,693 $ 14,135 $ 11,220 $ 40,223 $ 1,587 $ 86,440 Provision for credit losses 610 (1,687 ) 317 369 555 536 700 Charge-offs (44 ) (10 ) (6 ) — (1,957 ) (892 ) (2,909 ) Recoveries 44 1,288 9 1 238 280 1,860 Net charge-offs — 1,278 3 1 (1,719 ) (612 ) (1,049 ) Balance March 31, 2019 $ 16,192 $ 3,284 $ 14,455 $ 11,590 $ 39,059 $ 1,511 $ 86,091 Allowance for Credit Losses on Off-Balance Sheet Credit Exposures. The allowance also includes estimates of 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 for credit losses on off-balance sheet exposures 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 informed by historical analysis looking at utilization rates. The expected credit loss rates applied to the commitments expected to fund is informed by the general valuation allowance utilized for outstanding balances with the same underlying assumptions and drivers. As of March 31, 2020, the Company had $29.9 million in allowance for credit losses on off-balance sheet credit exposure, compared with $5.6 million as of December 31, 2019. This allowance for credit losses on off-balance sheet credit exposure is a separate line item on the Company’s consolidated balance sheet. As of March 31, 2020, the Company had $1.82 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, 2020 and 2019, respectively, the Company had $13.0 million and $14.8 million, in outstanding troubled debt restructurings. The following table presents information regarding the recorded investment of loans modified as troubled debt restructurings during the three months ended March 31, 2020 and 2019. Three Months Ended March 31, 2020 2019 Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment (Dollars in thousands) Troubled Debt Restructurings 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 — — — 1 14,783 14,783 Consumer and other — — — — — — Total — $ — $ — 1 $ 14,783 $ 14,783 As of March 31, 2020, 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, 2020, the Company did not add any loans as new troubled debt restructurings. For the three months ended March 31, 2019, the Company added one loan totaling $14.8 million as a new troubled debt restructuring, of which $14.8 million remained outstanding at March 31, 2019. The Company did not grant principal reductions on any restructured loans at the time of modification. These modifications did not have a material impact on the Company’s determination of the allowance for credit losses. Under the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”), banks may elect to deem that loan modifications do not result in troubled debt restructurings if they are (1) related to the novel strain of coronavirus disease (“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) December 31, 2020. 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 short-term (e.g., up to six months) modifications such as payment deferrals, 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 noted above do not include loans that are short-term modifications related to COVID-19.

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2020
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, 2020 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 306 $ — $ 306 Collateralized mortgage obligations — 266,467 — 266,467 Mortgage-backed securities — 48,482 — 48,482 Total $ — $ 315,255 $ — $ 315,255 Derivative financial instruments: Interest rate lock commitments $ — $ 1,420 $ — $ 1,420 Forward mortgage-backed securities trades — — — — Loan customer counterparty — 14,173 — 14,173 Financial institution counterparty — — — — Liabilities: Derivative financial instruments: Interest rate lock commitments $ — $ 3 $ — $ 3 Forward mortgage-backed securities trades — 1,483 — 1,483 Loan customer counterparty — — — — Financial institution counterparty — 14,173 — 14,173 As of December 31, 2019 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 471 $ — $ 471 Collateralized mortgage obligations — 235,773 — 235,773 Mortgage-backed securities — 51,419 — 51,419 Total available for sale securities $ — $ 287,663 $ — $ 287,663 Derivative financial instruments: Interest rate lock commitments $ — 305 $ — 305 Forward mortgage-backed securities trades — 3 — 3 Loan customer counterparty — 4,829 — 4,829 Financial institution counterparty — 240 — 240 Liabilities: Derivative financial instruments: Interest rate lock commitments $ — $ — $ — $ — Forward mortgage-backed securities trades — 83 — 83 Loan customer counterparty — 240 — 240 Financial institution counterparty — 4,829 — 4,829 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, 2020, the Company had additions to other real estate owned of $112 thousand, of which $92 thousand were outstanding as of March 31, 2020. For the three months ended March 31, 2020, the Company had additions to impaired loans of $11.5 million, all of which was still outstanding as of March 31, 2020. The remaining financial assets and liabilities measured at fair value on a non-recurring basis that were recorded in 2020 and remained outstanding at March 31, 2020 were not significant. The following tables present carrying and fair value information of financial instruments as of the dates indicated: As of March 31, 2020 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 381,458 $ 381,458 $ — $ — $ 381,458 Federal funds sold 676 676 — — 676 Held to maturity securities 7,980,240 — 8,136,374 — 8,136,374 Loans held for sale 65,035 — 65,035 — 65,035 Loans held for investment, net of allowance 17,021,192 — — 16,714,427 16,714,427 Loans held for investment - Warehouse Purchase Program 1,713,762 — 1,713,762 — 1,713,762 Other real estate owned 5,452 — 5,452 — 5,452 Liabilities Deposits: Noninterest-bearing $ 7,461,323 $ — $ 7,461,323 $ — $ 7,461,323 Interest-bearing 16,365,034 — 16,396,178 — 16,396,178 Other borrowings 1,338,429 — 1,338,686 — 1,338,686 Securities sold under repurchase agreements 344,695 — 344,739 — 344,739 Subordinated notes 125,585 — 125,732 — 125,732 As of December 31, 2019 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 573,589 $ 573,589 $ — $ — $ 573,589 Federal funds sold 519 519 — — 519 Held to maturity securities 8,282,393 — 8,303,851 — 8,303,851 Loans held for sale 80,959 — 80,959 — 80,959 Loans held for investment, net of allowance 17,124,156 — — 17,045,523 17,045,523 Loans held for investment - Warehouse Purchase Program 1,552,762 — 1,552,762 — 1,552,762 Other real estate owned 6,936 — 6,936 — 6,936 Liabilities Deposits: Noninterest-bearing $ 7,763,894 $ — $ 7,763,894 $ — $ 7,763,894 Interest-bearing 16,435,838 — 16,437,453 — 16,437,453 Other borrowings 1,303,730 — 1,303,941 — 1,303,941 Securities sold under repurchase agreements 377,294 — 377,302 — 377,302 Subordinated notes 125,804 — 125,743 — 125,743 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, 2020. 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, 2020
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, 2020 and the year ended December 31, 2019 were as follows: Goodwill Core Deposit Intangibles (Dollars in thousands) Balance as of December 31, 2018 $ 1,900,845 $ 32,883 Less: Amortization — (6,537 ) Add: LegacyTexas Merger 1,322,826 60,058 Balance as of December 31, 2019 3,223,671 86,404 Less: Amortization — (3,363 ) Add: Measurement period adjustment of LegacyTexas Merger (527 ) — Balance as of March 31, 2020 $ 3,223,144 $ 83,041 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, 2020, 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 $3.4 million and $1.3 million for the three months ended March 31, 2020 and 2019, respectively. The estimated aggregate future amortization expense for core deposit intangibles remaining as of March 31, 2020 is as follows (dollars in thousands): Remaining 2020 $ 9,806 2021 11,551 2022 10,336 2023 9,360 2024 8,699 Thereafter 33,289 Total $ 83,041

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	8. STOCK–BASED COMPENSATION At March 31, 2020, the Company had two stock-based employee compensation plan with awards outstanding. On March 3, 2020, Bancshares’ Board of Directors established the Prosperity Bancshares, Inc. 2020 Stock Incentive Plan (the “2020 Plan”), subject to approval by the Company’s shareholders. The Company’s shareholders approved the 2020 Plan at the annual meeting of 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, 2020, no options or other awards 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, 2020 , a total of 357,013 shares of common stock have been issued pursuant to vested awards ; a nd 506,362 shares of unvested restricted stock have been granted under the 2012 Plan . The Company does not plan to make any further awards pursuant to the 2012 Plan. As of March 31, 2020, the Company had no stock options outstanding. Stock-based compensation expense related to restricted stock was $3.3 million and $2.8 million during the three months ended March 31, 2020 and 2019, respectively. As of March 31, 2020, there was $14.8 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 1.54 years.

Contractual Obligations and Off

Contractual Obligations and Off-Balance Sheet Items	3 Months Ended
	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Contractual Obligations and Off-Balance Sheet Items	9. CONTRACTUAL OBLIGATIONS AND OFF-BALANCE SHEET ITEMS Contractual Obligations The Company’s contractual obligations and other commitments to make future payments as of March 31, 2020 (other than deposit obligations and securities sold under repurchase agreements) are summarized below. The Company’s future cash payments associated with its contractual obligations pursuant to its subordinated notes and Federal Home Loan Bank (“FHLB”) advances and notes payable as of March 31, 2020 are summarized below. The future interest payments were calculated using the current rate in effect at March 31, 2020. Payments for the subordinated notes include interest of $40.3 million that will be due over the future periods. Payments for FHLB notes payable include interest of $299 thousand that will be paid over the future periods. The payments do not include pre-payment options that may be available to the Company. 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) Subordinated notes $ 6,875 $ 13,750 $ 13,750 $ 130,958 $ 165,333 Federal Home Loan Bank advances and notes payable 1,336,237 1,642 596 29 1,338,504 Total $ 1,343,112 $ 15,392 $ 14,346 $ 130,987 $ 1,503,837 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 does not have any sublease arrangements. As of March 31, 2020, operating lease ROU assets and lease liabilities were approximately $54 million. ROU assets and lease liabilities were classified as other assets and other liabilities, respectively. As of March 31, 2020, the weighted average remaining lease terms of the Company’s operating leases were 8.0 years. The weighted average discount rate used to determine the lease liabilities as of March 31, 2020 for the Company’s operating leases was 2.49%. Cash paid for the Company’s operating leases for the three months ended March 31, 2020 and March 31, 2019 was $3.6 million and $1.4 million, respectively. The Company obtained $1.5 million in ROU assets in exchange for lease liabilities for three operating leases during the three months ended March 31, 2020. The Company’s future undiscounted cash payments associated with its operating leases as of March 31, 2020 are summarized below (dollars in thousands). Remaining 2020 $ 7,660 2021 9,523 2022 8,998 2023 8,250 2024 7,369 2025 6,978 Thereafter 18,247 Total undiscounted lease payments $ 67,025 The following table presents a summary of non-cancelable future operating lease commitments as of December 31, 2019 (dollars in thousands): 2020 $ 10,137 2021 9,169 2022 8,641 2023 7,998 2024 7,119 Thereafter 24,996 Total non-cancelable lease payments $ 68,060 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, 2020 are summarized below. Since commitments associated with letters of credit, unused capacity of Warehouse Purchase Program loans, allowance for credit losses on off-balance sheet credit exposure 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 $ 104,592 $ 10,531 $ 1,619 $ — $ 116,742 Unused capacity on Warehouse Purchase Program loans 858,238 — — — 858,238 Commitments to extend credit 1,854,275 936,045 291,181 1,238,653 4,320,154 Total $ 2,817,105 $ 946,576 $ 292,800 $ 1,238,653 $ 5,295,134 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, 2020 and December 31, 2019, 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 exposure” on the Company’s consolidated balance sheet, totaled $29.9 million and $5.6 million, respectively.

Other Comprehensive Income

Other Comprehensive Income	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 Before Tax Amount Tax Effect Net of Tax Amount Before Tax Amount Tax Effect Net of Tax Amount (Dollars in thousands) Other comprehensive (loss) income: Securities available for sale: Change in unrealized gain during period $ (4,183 ) $ 878 $ (3,305 ) $ 503 $ (106 ) $ 397 Total securities available for sale (4,183 ) 878 (3,305 ) 503 (106 ) 397 Total other comprehensive (loss) income $ (4,183 ) $ 878 $ (3,305 ) $ 503 $ (106 ) $ 397 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 (Dollars in thousands) Balance at December 31, 2019 $ 602 $ 602 Other comprehensive loss (3,305 ) (3,305 ) Balance at March 31, 2020 $ (2,703 ) $ (2,703 ) Balance at December 31, 2018 $ 310 $ 310 Other comprehensive income 397 397 Balance at March 31, 2019 $ 707 $ 707

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2020
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, 2020 and December 31, 2019. March 31, 2020 December 31, 2019 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) Interest rate lock commitments $ 55,892 $ 1,420 $ 3 $ 9,438 $ 305 $ — Forward mortgage-backed securities trades 74,250 — 1,483 40,750 3 83 Commercial loan interest rate swaps and caps: Loan customer counterparty 230,760 14,173 — 231,345 4,829 240 Financial institution counterparty 230,760 — 14,173 231,345 240 4,829 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, 2020 and December 31, 2019 are presented in the following table. Weighted-Average Interest Rate March 31, 2020 December 31, 2019 Received Paid Received Paid Loan customer counterparty 3.18 % 2.36 % 3.42 % 2.86 % 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 $14.2 million at March 31, 2020 and $4.8 million at December 31, 2019. 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, 2020. 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 of $14.3 million at March 31, 2020 and $9.3 The initial and subsequent changes in the fair value of IRLCs and the forward sales of mortgage-back 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, 2020 and 2019 was as follows: Three Months Ended March 31, Derivatives not designated as hedging instruments 2020 2019 Interest rate lock commitments $ 1,112 $ — Forward mortgage-backed securities trades (1,937 ) —

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Acquisitions	12. ACQUISITIONS Acquisitions are an integral part of the Company’s growth strategy. All acquisitions were accounted for using the acquisition method of accounting. Accordingly, the assets and liabilities of the acquired entities were recorded at their fair values at the acquisition date. The excess of the purchase price over the estimated fair value of the net assets for tax-free acquisitions was recorded as goodwill, none of which is deductible for tax purposes. The excess of the purchase price over the estimated fair value of the net assets for taxable acquisitions was also recorded as goodwill, and is deductible for tax purposes. The identified core deposit intangibles for each acquisition are being amortized using a non-pro rata basis over an estimated life of 10 to 15 years. The results of operations for each acquisition have been included in the Company’s consolidated financial results beginning on the respective acquisition date. The measurement period for the Company to determine the fair values of acquired identifiable assets and assumed liabilities will end at the earlier of (1) twelve months from the date of the acquisition or (2) as soon as the Company receives the information it was seeking about facts and circumstances that existed as of the acquisition date or learns that more information is not obtainable. The following acquisitions were completed on the dates indicated: 2019 Acquisition Merger with LegacyTexas Financial Group, Inc. On November 1, 2019, LegacyTexas Financial Group, Inc. merged into Prosperity Bancshares and LegacyTexas Bank merged into the Bank. LegacyTexas was headquartered in Plano, Texas and operated 42 locations in 19 North Texas cities in and around the Dallas-Fort Worth area. As of September 30, 2019, LegacyTexas, on a consolidated basis, reported total assets of $10.5 billion, total gross loans of $9.1 billion, total deposits of $6.5 billion and shareholders’ equity of $1.2 billion. Pursuant to the terms of the merger agreement, Bancshares issued 26,228,148 shares of Bancshares common stock, with a closing price of $69.02 per share on November 1, 2019, plus $318.0 million in cash, comprised of $308.6 million in cash and $9.4 million in cash for taxes withheld, for all outstanding shares of LegacyTexas. The assets and liabilities of LegacyTexas were recorded on the consolidated balance sheet at estimated fair value on the acquisition date. As of March 31, 2020, the following table presents the amounts recorded on the consolidated balance sheet on the acquisition date (dollars in thousands). Initially Recorded at Acquisition Date Measurements Period Adjustments Adjusted Values as of March 31, 2020 Fair value of consideration paid: Common stock issued (26,228,148 shares) $ 1,810,267 $ — $ 1,810,267 Cash 318,018 — 318,018 Total consideration paid $ 2,128,285 $ — $ 2,128,285 Fair value of assets acquired: Cash and due from banks $ 228,649 $ — $ 228,649 Securities held to maturity 472,933 — 472,933 Loans held for sale 60,818 — 60,818 Loans held for investment 6,771,080 — 6,771,080 Loans held for investment - Warehouse Purchase Program 1,693,049 — 1,693,049 Bank premises and equipment 67,347 — 67,347 Other real estate owned 4,876 — 4,876 Core deposit intangibles 60,058 — 60,058 Federal Home Loan Bank stock 117,939 — 117,939 Bank owned life insurance and other assets 242,592 (139 ) 242,453 Total assets acquired 9,719,341 (139 ) 9,719,202 Fair value of liabilities assumed: Deposits 6,434,732 — 6,434,732 Other borrowings 2,078,682 — 2,078,682 Securities sold under repurchase agreements 57,670 — 57,670 Trust preferred securities 15,376 — 15,376 Subordinated notes 125,950 — 125,950 Other liabilities 201,472 (666 ) 200,806 Total liabilities assumed 8,913,882 (666 ) 8,913,216 Fair value of net assets acquired $ 805,459 $ 527 $ 805,986 Goodwill resulting from acquisition $ 1,322,826 $ (527 ) $ 1,322,299 The measurement period adjustments noted in the table above was a result of information obtained subsequent to the Company’s initial reporting of provisional fair values but prior to finalizing the fair values in accordance with ASC 805, Business Combinations. Such information was determined to be a condition in existence as of acquisition date. As of March 31, 2020, the Company recognized goodwill of $1.32 billion , which is subject to subsequent fair value adjustments Merger Related Expenses: The Company incurred $544 thousand and $46.4 million of pre-tax merger related expenses during the three months ended March 31, 2020 and year ended December 31, 2019, respectively. The merger expenses are reflected on the Company’s income statement for the applicable periods under Merger related expenses, which consist of salaries and benefits, data processing and professional and legal fees. Pro Forma Information : Operations of LegacyTexas have been included in the consolidated financial statements since November 1, 2019. The amount of revenue (net interest income plus non-interest income) derived from LegacyTexas since the acquisition date included in the consolidated income statement for the three months ended March 31, 2020 and year ended December 31, 2019 was approximately $106.2 million and $79.7 million, respectively. The following pro forma information presents the results of operations for the three months ended March 31, 2019, as if the Merger had occurred on January 1, 2019 (dollars in thousands, except per share amounts). Three Months Ended March 31, 2019 Net interest income $ 265,247 Net income 95,769 Basic earnings per share 1.00 Diluted earnings per share 1.00 The above pro forma results are presented for illustrative purposes and are not intended to represent or be indicative of the actual results of operations of the merged companies that would have been achieved had the Merger occurred on January 1, 2019, nor are they intended to represent or be indicative of future results of operations. The pro forma results do not include expected operating cost savings as a result of the acquisition. These pro forma results require significant estimates and judgments particularly as it relates to valuation and accretion of income associated with acquired loans. Pro forma adjustments principally included: • Reversing interest income and interest expense as previously recorded by LegacyTexas and recording interest income and interest expense based on impact of estimated fair values of the acquired interest-earning assets and assumed interest-bearing liabilities; • Reversing core deposit intangible amortization as previously recorded by LegacyTexas and recording amortization expense as it relates to the core deposit intangible recognized from the acquisition; and • Reporting merger related expenses as if they were incurred on January 1, 2019.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	13. SUBSEQUENT EVENTS COVID-19 Pandemic In December 2019, COVID-19 was first reported in Wuhan, Hubei Province, China. On March 11, 2020, the World Health Organization declared COVID-19 a pandemic, and on March 13, the U.S. President announced a national emergency relating to the pandemic. On March 13, the Texas governor signed a proclamation certifying that COVID-19 poses an imminent threat of disaster in the state and declaring a state of disaster for all counties in Texas. The Bank is considered an essential business and is closely monitoring the latest developments regarding COVID-19. The health and safety of the Bank’s associates, customers, and communities are of utmost importance, and the Bank remains committed to providing uninterrupted service. Additionally, the Bank has continuity plans in place to ensure critical operations are able to continue without disruption. The COVID-19 pandemic has resulted in significant economic uncertainties that could negatively impact the Company’s operating income, financial condition and cash flows. As a result of COVID-19, the CARES Act was signed into law on March 27, 2020 by the President of the United States. The CARES Act provides assistance for American workers, families and small businesses. The Paycheck Protection Program (“PPP”) established by the CARES Act, is implemented by the Small Business Administration (“SBA”) with support from the Department of the Treasury. This program provides small businesses with funds to pay up to 8 weeks of payroll costs including benefits. Funds can also be used to pay interest on mortgages, rent, and utilities. The PPP loans have a two-year . .

New Accounting Standards (Polic

New Accounting Standards (Policies)	3 Months Ended
	Mar. 31, 2020
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 (ii) 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 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. ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments (“ASC 326”).” On January 1, 2020 the Company adopted ASU 2016-13 which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (“CECL”) methodology. CECL requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of CECL is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. The Company adopted ASU 2016-13 using the modified-retrospective method for all financial assets measured at amortized cost and off-balance sheet credit exposures. Reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior periods are reported with previously applicable GAAP. Upon adoption of ASU 2016-13, the Company recognized an increase in allowance for credit losses for loans of $108.7 million, of which $102.5 million was related to LegacyTexas Financial Group, Inc. (“LegacyTexas”), which merged into Bancshares on November 1, 2019, and an increase in allowance for credit losses for off-balance sheet credit exposures of $24.4 million, of which $6.3 million was related to LegacyTexas, with a corresponding decrease in retained earnings (pre-tax). Additionally, the Company adopted ASU 2016-13 using the prospective transition approach for financial assets purchased with credit deterioration. The Company recognized an increase in the allowance for credit losses for loans of $131.8 million, of which $130.3 million was related to LegacyTexas, due to the reclass of purchased credit deteriorated discounts as the result of adopting ASU 2016-13. See Note 5 “Loans and Allowance for Credit Losses” for additional information. The Company recognized no allowance for credit losses related to debt securities. See Note 4 “Securities” for additional information. The following table illustrates the impact of adopting ASU 2016-13: January 1, 2020 As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption (Dollars in thousands) Assets: Loans Construction, land development and other land loans $ 28,729 $ 14,654 $ 14,075 Agriculture and agriculture real estate (includes farmland) 5,768 2,971 2,797 1-4 family (includes home equity) 23,544 15,277 8,267 Commercial real estate (includes multi-family residential) 61,322 12,332 48,990 Commercial and industrial 180,069 40,445 139,624 Consumer and other 28,575 1,790 26,785 Allowance for credit losses on loans $ 328,007 $ 87,469 $ 240,538 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 29,947 $ 5,599 $ 24,348

Income Per Common Share (Tables

Income Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 Amount Per Share Amount Amount Per Share Amount (Amounts in thousands, except per share data) Net income $ 130,848 $ 82,402 Basic: Weighted average shares outstanding 94,371 $ 1.39 69,847 $ 1.18 Diluted: Weighted average shares outstanding 94,371 $ 1.39 69,847 $ 1.18

New Accounting Standards (Table

New Accounting Standards (Tables)	3 Months Ended
	Mar. 31, 2020
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Schedule of Impact of Adopting ASU 2016-13	The following table illustrates the impact of adopting ASU 2016-13: January 1, 2020 As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption (Dollars in thousands) Assets: Loans Construction, land development and other land loans $ 28,729 $ 14,654 $ 14,075 Agriculture and agriculture real estate (includes farmland) 5,768 2,971 2,797 1-4 family (includes home equity) 23,544 15,277 8,267 Commercial real estate (includes multi-family residential) 61,322 12,332 48,990 Commercial and industrial 180,069 40,445 139,624 Consumer and other 28,575 1,790 26,785 Allowance for credit losses on loans $ 328,007 $ 87,469 $ 240,538 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 29,947 $ 5,599 $ 24,348

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 305 $ 1 $ — $ 306 Collateralized mortgage obligations 269,777 175 (3,485 ) 266,467 Mortgage-backed securities 48,594 639 (751 ) 48,482 Total $ 318,676 $ 815 $ (4,236 ) $ 315,255 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 6,959 $ 76 $ — $ 7,035 States and political subdivisions 208,744 7,172 (563 ) 215,353 Collateralized mortgage obligations 184,540 4,156 (39 ) 188,657 Mortgage-backed securities 7,579,997 146,864 (1,532 ) 7,725,329 Total $ 7,980,240 $ 158,268 $ (2,134 ) $ 8,136,374 December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) Available for Sale States and political subdivisions $ 470 $ 1 $ — $ 471 Collateralized mortgage obligations 235,222 690 (139 ) 235,773 Mortgage-backed securities 51,209 659 (449 ) 51,419 Total $ 286,901 $ 1,350 $ (588 ) $ 287,663 Held to Maturity U.S. Treasury securities and obligations of U.S. Government agencies $ 13,933 $ 58 $ — $ 13,991 States and political subdivisions 238,347 7,632 (189 ) 245,790 Collateralized mortgage obligations 203,470 1,115 (373 ) 204,212 Mortgage-backed securities 7,826,643 48,060 (34,845 ) 7,839,858 Total $ 8,282,393 $ 56,865 $ (35,407 ) $ 8,303,851
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, 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 $ 145,162 $ (3,473 ) $ 1,725 $ (12 ) $ 146,887 $ (3,485 ) Mortgage-backed securities 32,690 (751 ) 7 — 32,697 (751 ) Total $ 177,852 $ (4,224 ) $ 1,732 $ (12 ) $ 179,584 $ (4,236 ) Held to Maturity States and political subdivisions $ 52,617 $ (563 ) $ — $ — $ 52,617 $ (563 ) Collateralized mortgage obligations 9,426 (39 ) — — 9,426 (39 ) Mortgage-backed securities 41,092 (525 ) 210,809 (1,007 ) 251,901 (1,532 ) Total $ 103,135 $ (1,127 ) $ 210,809 $ (1,007 ) $ 313,944 $ (2,134 ) December 31, 2019 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 $ 50,245 $ (136 ) $ 1,818 $ (3 ) $ 52,063 $ (139 ) Mortgage-backed securities 34,901 (449 ) 10 — 34,911 (449 ) Total $ 85,146 $ (585 ) $ 1,828 $ (3 ) $ 86,974 $ (588 ) Held to Maturity States and political subdivisions $ 58,329 $ (183 ) $ 3,241 $ (6 ) $ 61,570 $ (189 ) Collateralized mortgage obligations 54,890 (373 ) — — 54,890 (373 ) Mortgage-backed securities 947,314 (3,017 ) 3,110,765 (31,828 ) 4,058,079 (34,845 ) Total $ 1,060,533 $ (3,573 ) $ 3,114,006 $ (31,834 ) $ 4,174,539 $ (35,407 )
Investment Securities by Contractual Maturity	The amortized cost and fair value of investment securities at March 31, 2020, 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 $ 31,833 $ 31,993 $ 305 $ 306 Due after one year through five years 119,381 123,392 — — Due after five years through ten years 57,735 60,219 — — Due after ten years 6,754 6,784 — — Subtotal 215,703 222,388 305 306 Mortgage-backed securities and collateralized mortgage obligations 7,764,537 7,913,986 318,371 314,949 Total $ 7,980,240 $ 8,136,374 $ 318,676 $ 315,255

Loans and Allowance for Credi_2

Loans and Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 December 31, 2019 (Dollars in thousands) Residential mortgage loans held for sale $ 65,035 $ 80,959 Commercial and industrial 3,218,763 3,205,595 Real estate: Construction, land development and other land loans 2,051,021 2,064,167 1-4 family residential (includes home equity) 4,444,106 4,306,452 Commercial real estate (includes multi-family residential) 6,576,213 6,556,285 Farmland 467,372 495,558 Agriculture 167,923 185,297 Consumer and other 423,000 398,271 Total loans held for investment, excluding Warehouse Purchase Program 17,348,398 17,211,625 Warehouse Purchase Program 1,713,762 1,552,762 Total loans, including Warehouse Purchase Program $ 19,127,195 $ 18,845,346
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, 2020 As of and for the year ended December (Dollars in thousands) Beginning balance on January 1 $ 4,152 $ 1,923 New loans — 1 Transfers — 2,500 Repayments (79 ) (272 ) Ending balance $ 4,073 $ 4,152
Aging Analysis of Past Due Loans	An aging analysis of past due loans, segregated by category of loan, is presented below: March 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 $ 70,850 $ — $ 70,850 $ 1,125 $ 1,979,046 $ 2,051,021 Warehouse Purchase Program loans — — — — 1,713,762 1,713,762 Agriculture and agriculture real estate (includes farmland) 3,017 868 3,885 28 631,382 635,295 1-4 family (includes home equity) (1) 39,525 2,213 41,738 26,632 4,440,771 4,509,141 Commercial real estate (includes multi-family residential) 15,284 169 15,453 14,685 6,546,075 6,576,213 Commercial and industrial 7,653 2 7,655 15,720 3,195,388 3,218,763 Consumer and other 11,059 3 11,062 4 411,934 423,000 Total $ 147,388 $ 3,255 $ 150,643 $ 58,194 $ 18,918,358 $ 19,127,195 December 31, 2019 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 $ 16,470 $ — $ 16,470 $ 1,142 $ 2,046,555 $ 2,064,167 Warehouse Purchase Program loans — — — — 1,552,762 1,552,762 Agriculture and agriculture real estate (includes farmland) 466 — 466 103 680,286 680,855 1-4 family (includes home equity) (1) 43,884 441 44,325 24,413 4,318,673 4,387,411 Commercial real estate (includes multi-family residential) 10,669 — 10,669 12,714 6,532,902 6,556,285 Commercial and industrial 7,249 — 7,249 16,809 3,181,537 3,205,595 Consumer and other 1,708 — 1,708 62 396,501 398,271 Total $ 80,446 $ 441 $ 80,887 $ 55,243 $ 18,709,216 $ 18,845,346 (1) Includes $65.0 million and $81.0 million of residential mortgage loans held for sale at March 31, 2020 and December 31, 2019, respectively.
Non-performing Assets	The following table presents information regarding nonperforming assets as of the dates indicated: March 31, 2020 December 31, 2019 (Dollars in thousands) Nonaccrual loans (1) (2) $ 58,194 $ 55,243 Accruing loans 90 or more days past due 3,255 441 Total nonperforming loans 61,449 55,684 Repossessed assets 278 323 Other real estate 5,452 6,936 Total nonperforming assets $ 67,179 $ 62,943 Nonperforming assets to total loans and other real estate 0.35 % 0.33 % Nonperforming assets to total loans, excluding Warehouse Purchase Program loans, and other real estate 0.39 % 0.36 % (1) Includes troubled debt restructurings of $13.0 million and $13.6 million as of March 31, 2020 and December 31, 2019, 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, 2020 and December 31, 2019 . March 31, 2020 December 31, 2019 (Dollars in thousands) PCD loans: Outstanding balance $ 355,160 $ 410,785 Discount (1) (29,460 ) (167,320 ) (2) Recorded investment $ 325,700 $ 243,465 (1) ASU 2016-13 became effective for the Company on January 1, 2020. (2) Includes $131.8 million in PCD loans credit discount. March 31, 2020 December 31, 2019 (Dollars in thousands) Non-PCD loans: Outstanding balance $ 5,744,368 $ 6,102,540 Discount (87,613 ) (110,130 ) Recorded investment $ 5,656,755 $ 5,992,410
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, 2020 and 2019 were as follows: Three Months Ended March 31, 2020 2019 (Dollars in thousands) Balance at beginning of period $ 35,654 $ 1,534 Adjustments (175 ) 19 Accretion (6,019 ) (319 ) Balance at March 31, $ 29,460 $ 1,234 Changes in the discount accretion for Non-PCD loans for the three months ended March 31, 2020 and 2019 were as follows: Three Months Ended March 31, 2020 2019 (Dollars in thousands) Balance at beginning of period $ 110,130 $ 14,833 Accretion charge-offs (54 ) — Accretion (22,463 ) (1,474 ) Balance at March 31, $ 87,613 $ 13,359
Risk Grade and Category of Loan	The following table presents loans by risk grade and category of loan at March 31, 2020. Impaired loans include loans in risk grades 7, 8 and 9, as well as any PCD loan that has deteriorated since the acquisition date. Term Loans Amortized Cost Basis by Origination Year 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Construction, Land Development and Other Land Loans Grade 1 $ — $ — $ — $ — $ — $ 29 $ — $ — $ 29 Grade 2 — 1,119 — 90 135 362 — — 1,706 Grade 3 215,615 818,291 437,168 125,916 28,173 64,486 132,231 624 1,822,504 Grade 4 3,829 28,601 31,715 122,176 3,763 9,340 12,566 — 211,990 Grade 5 — — 2,564 — — 363 — — 2,927 Grade 6 — — — — 602 1,688 — — 2,290 Grade 7 — — — — — 390 734 — 1,124 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — 7,875 129 447 — — — — 8,451 Total $ 219,444 $ 855,886 $ 471,576 $ 248,629 $ 32,673 $ 76,658 $ 145,531 $ 624 $ 2,051,021 Agriculture and Agriculture Real Estate (includes Farmland) Grade 1 $ 167 $ 2,099 $ 298 $ 258 $ — $ 1 $ 9,019 $ — $ 11,842 Grade 2 — — 13 358 8 1,756 — — 2,135 Grade 3 26,553 100,074 78,662 62,508 59,832 126,263 82,030 4 535,926 Grade 4 5,561 10,223 4,704 2,555 6,860 23,985 17,707 1,158 72,753 Grade 5 637 4,190 329 — — 990 2,929 — 9,075 Grade 6 1,331 — — — 186 188 — — 1,705 Grade 7 — — 28 — — — — — 28 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 978 223 — — — 312 318 — 1,831 Total $ 35,227 $ 116,809 $ 84,034 $ 65,679 $ 66,886 $ 153,495 $ 112,003 $ 1,162 $ 635,295 1-4 Family (includes Home Equity) (1) Grade 1 $ 100 $ — $ — $ — $ — $ — $ 204 $ — $ 304 Grade 2 292 775 1,018 895 265 9,918 1,136 — 14,299 Grade 3 255,393 1,011,615 715,736 589,506 556,826 1,097,425 146,389 1,470 4,374,360 Grade 4 724 14,698 7,402 12,131 10,200 33,866 1,636 521 81,178 Grade 5 — 224 2,052 1,282 111 2,112 — — 5,781 Grade 6 — 29 — 333 138 1,948 24 — 2,472 Grade 7 — 1,787 1,173 2,501 1,159 13,834 3,509 — 23,963 Grade 8 — — — — 10 93 — — 103 Grade 9 — — — — — — — — — PCD Loans — — — — 264 5,366 1,051 — 6,681 Total $ 256,509 $ 1,029,128 $ 727,381 $ 606,648 $ 568,973 $ 1,164,562 $ 153,949 $ 1,991 $ 4,509,141 Term Loans Amortized Cost Basis by Origination Year 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Commercial Real Estate (includes Multi-Family Residential) Grade 1 $ — $ — $ — $ — $ — $ 1,385 $ — $ — $ 1,385 Grade 2 5,862 935 — 7,948 209 4,986 — — 19,940 Grade 3 127,368 1,161,018 1,183,252 1,106,578 653,077 1,362,652 120,075 — 5,714,020 Grade 4 9,140 34,890 67,523 129,964 164,600 246,546 17,749 — 670,412 Grade 5 — — 2,259 12,909 4,251 14,463 — — 33,882 Grade 6 — 3,745 1,250 196 3,239 11,153 1,500 — 21,083 Grade 7 — 6 — 17 14,412 224 — — 14,659 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 27,593 21,709 5,476 27,168 578 18,308 — — 100,832 Total $ 169,963 $ 1,222,303 $ 1,259,760 $ 1,284,780 $ 840,366 $ 1,659,717 $ 139,324 $ — $ 6,576,213 Commercial and Industrial Grade 1 $ 9,544 $ 19,031 $ 5,023 $ 1,221 $ 921 $ 46,114 $ 22,818 $ 35 $ 104,707 Grade 2 341 221 1,280 1,697 1,497 1,534 85,570 — 92,140 Grade 3 66,617 428,024 246,098 125,966 97,689 164,771 1,337,870 518 2,467,553 Grade 4 17,653 56,789 24,562 24,629 11,193 32,869 132,853 483 301,031 Grade 5 2,087 18,781 840 241 376 21 4,298 — 26,644 Grade 6 25 581 2,828 — 122 2,509 27,007 — 33,072 Grade 7 — 758 12,577 872 929 284 99 — 15,519 Grade 8 — — — — 13 — — — 13 Grade 9 — — — — — — — — — PCD Loans 996 22,175 9,685 11,769 3,750 1,140 128,569 — 178,084 Total $ 97,263 $ 546,360 $ 302,893 $ 166,395 $ 116,490 $ 249,242 $ 1,739,084 $ 1,036 $ 3,218,763 Consumer and Other Grade 1 $ 6,476 $ 20,300 $ 6,398 $ 3,273 $ 1,913 $ 1,192 $ 1,393 $ — $ 40,945 Grade 2 1,707 10,878 1,011 41,282 1,676 — 1,467 — 58,021 Grade 3 13,862 80,824 39,194 27,396 9,741 19,122 72,968 147 263,254 Grade 4 1,293 4,925 31 5 120 174 21,057 — 27,605 Grade 5 — — 72 18 — — 1,717 — 1,807 Grade 6 — 1,534 — — — — 1 — 1,535 Grade 7 — 1 7 — — 1 3 — 12 Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans 4,385 8,947 — — — — 16,489 — 29,821 Total $ 27,723 $ 127,409 $ 46,713 $ 71,974 $ 13,450 $ 20,489 $ 115,095 $ 147 $ 423,000 Term Loans Amortized Cost Basis by Origination Year 2020 2019 2018 2017 2016 Prior Revolving Loans Revolving Loans Converted to Term Loans Total (Dollars in thousands) Warehouse Purchase Program Grade 1 $ — $ — $ — $ — $ — $ — $ — $ — $ — Grade 2 — — — — — — — — — Grade 3 1,713,762 — — — — — — — 1,713,762 Grade 4 — — — — — — — — — Grade 5 — — — — — — — — — Grade 6 — — — — — — — — — Grade 7 — — — — — — — — — Grade 8 — — — — — — — — — Grade 9 — — — — — — — — — PCD Loans — — — — — — — — — Total $ 1,713,762 $ — $ — $ — $ — $ — $ — $ — $ 1,713,762 Total Grade 1 $ 16,287 $ 41,430 $ 11,719 $ 4,752 $ 2,834 $ 48,721 $ 33,434 $ 35 $ 159,212 Grade 2 8,202 13,928 3,322 52,270 3,790 18,556 88,173 — 188,241 Grade 3 2,419,170 3,599,846 2,700,110 2,037,870 1,405,338 2,834,719 1,891,563 2,763 16,891,379 Grade 4 38,200 150,126 135,937 291,460 196,736 346,780 203,568 2,162 1,364,969 Grade 5 2,724 23,195 8,116 14,450 4,738 17,949 8,944 — 80,116 Grade 6 1,356 5,889 4,078 529 4,287 17,486 28,532 — 62,157 Grade 7 — 2,552 13,785 3,390 16,500 14,733 4,345 — 55,305 Grade 8 — — — — 23 93 — — 116 Grade 9 — — — — — — — — — PCD Loans 33,952 60,929 15,290 39,384 4,592 25,126 146,427 — 325,700 Total $ 2,519,891 $ 3,897,895 $ 2,892,357 $ 2,444,105 $ 1,638,838 $ 3,324,163 $ 2,404,986 $ 4,960 $ 19,127,195 (1) Includes $65.0 million of residential mortgage loans held for sale at March 31, 2020.
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, 2020 and 2019. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. 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 Beginning balance, prior to adoption of ASC 326 $ 14,654 $ 2,971 $ 15,277 $ 12,332 $ 40,445 $ 1,790 $ 87,469 Impact of adoption ASC 326 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 Three Months Ended Balance December 31, 2018 $ 15,582 $ 3,693 $ 14,135 $ 11,220 $ 40,223 $ 1,587 $ 86,440 Provision for credit losses 610 (1,687 ) 317 369 555 536 700 Charge-offs (44 ) (10 ) (6 ) — (1,957 ) (892 ) (2,909 ) Recoveries 44 1,288 9 1 238 280 1,860 Net charge-offs — 1,278 3 1 (1,719 ) (612 ) (1,049 ) Balance March 31, 2019 $ 16,192 $ 3,284 $ 14,455 $ 11,590 $ 39,059 $ 1,511 $ 86,091
Troubled Debt Restructurings	The following table presents information regarding the recorded investment of loans modified as troubled debt restructurings during the three months ended March 31, 2020 and 2019. Three Months Ended March 31, 2020 2019 Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Loans Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment (Dollars in thousands) Troubled Debt Restructurings 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 — — — 1 14,783 14,783 Consumer and other — — — — — — Total — $ — $ — 1 $ 14,783 $ 14,783

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 306 $ — $ 306 Collateralized mortgage obligations — 266,467 — 266,467 Mortgage-backed securities — 48,482 — 48,482 Total $ — $ 315,255 $ — $ 315,255 Derivative financial instruments: Interest rate lock commitments $ — $ 1,420 $ — $ 1,420 Forward mortgage-backed securities trades — — — — Loan customer counterparty — 14,173 — 14,173 Financial institution counterparty — — — — Liabilities: Derivative financial instruments: Interest rate lock commitments $ — $ 3 $ — $ 3 Forward mortgage-backed securities trades — 1,483 — 1,483 Loan customer counterparty — — — — Financial institution counterparty — 14,173 — 14,173 As of December 31, 2019 Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets: Available for sale securities: States and political subdivisions $ — $ 471 $ — $ 471 Collateralized mortgage obligations — 235,773 — 235,773 Mortgage-backed securities — 51,419 — 51,419 Total available for sale securities $ — $ 287,663 $ — $ 287,663 Derivative financial instruments: Interest rate lock commitments $ — 305 $ — 305 Forward mortgage-backed securities trades — 3 — 3 Loan customer counterparty — 4,829 — 4,829 Financial institution counterparty — 240 — 240 Liabilities: Derivative financial instruments: Interest rate lock commitments $ — $ — $ — $ — Forward mortgage-backed securities trades — 83 — 83 Loan customer counterparty — 240 — 240 Financial institution counterparty — 4,829 — 4,829
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, 2020 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 381,458 $ 381,458 $ — $ — $ 381,458 Federal funds sold 676 676 — — 676 Held to maturity securities 7,980,240 — 8,136,374 — 8,136,374 Loans held for sale 65,035 — 65,035 — 65,035 Loans held for investment, net of allowance 17,021,192 — — 16,714,427 16,714,427 Loans held for investment - Warehouse Purchase Program 1,713,762 — 1,713,762 — 1,713,762 Other real estate owned 5,452 — 5,452 — 5,452 Liabilities Deposits: Noninterest-bearing $ 7,461,323 $ — $ 7,461,323 $ — $ 7,461,323 Interest-bearing 16,365,034 — 16,396,178 — 16,396,178 Other borrowings 1,338,429 — 1,338,686 — 1,338,686 Securities sold under repurchase agreements 344,695 — 344,739 — 344,739 Subordinated notes 125,585 — 125,732 — 125,732 As of December 31, 2019 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Assets Cash and due from banks $ 573,589 $ 573,589 $ — $ — $ 573,589 Federal funds sold 519 519 — — 519 Held to maturity securities 8,282,393 — 8,303,851 — 8,303,851 Loans held for sale 80,959 — 80,959 — 80,959 Loans held for investment, net of allowance 17,124,156 — — 17,045,523 17,045,523 Loans held for investment - Warehouse Purchase Program 1,552,762 — 1,552,762 — 1,552,762 Other real estate owned 6,936 — 6,936 — 6,936 Liabilities Deposits: Noninterest-bearing $ 7,763,894 $ — $ 7,763,894 $ — $ 7,763,894 Interest-bearing 16,435,838 — 16,437,453 — 16,437,453 Other borrowings 1,303,730 — 1,303,941 — 1,303,941 Securities sold under repurchase agreements 377,294 — 377,302 — 377,302 Subordinated notes 125,804 — 125,743 — 125,743

Goodwill and Core Deposit Int_2

Goodwill and Core Deposit Intangibles (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 and the year ended December 31, 2019 were as follows: Goodwill Core Deposit Intangibles (Dollars in thousands) Balance as of December 31, 2018 $ 1,900,845 $ 32,883 Less: Amortization — (6,537 ) Add: LegacyTexas Merger 1,322,826 60,058 Balance as of December 31, 2019 3,223,671 86,404 Less: Amortization — (3,363 ) Add: Measurement period adjustment of LegacyTexas Merger (527 ) — Balance as of March 31, 2020 $ 3,223,144 $ 83,041
Estimated Aggregate Future Amortization Expense for Core Deposit Intangibles	The estimated aggregate future amortization expense for core deposit intangibles remaining as of March 31, 2020 is as follows (dollars in thousands): Remaining 2020 $ 9,806 2021 11,551 2022 10,336 2023 9,360 2024 8,699 Thereafter 33,289 Total $ 83,041

Contractual Obligations and O_2

Contractual Obligations and Off-Balance Sheet Items (Tables)	3 Months Ended
	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of Contractual Obligations and Other Commitments	The Company’s contractual obligations and other commitments to make future payments as of March 31, 2020 (other than deposit obligations and securities sold under repurchase agreements) are summarized below. 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) Subordinated notes $ 6,875 $ 13,750 $ 13,750 $ 130,958 $ 165,333 Federal Home Loan Bank advances and notes payable 1,336,237 1,642 596 29 1,338,504 Total $ 1,343,112 $ 15,392 $ 14,346 $ 130,987 $ 1,503,837
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, 2020 are summarized below (dollars in thousands). Remaining 2020 $ 7,660 2021 9,523 2022 8,998 2023 8,250 2024 7,369 2025 6,978 Thereafter 18,247 Total undiscounted lease payments $ 67,025
Summary of Non-Cancelable Future Operating Lease Commitments	The following table presents a summary of non-cancelable future operating lease commitments as of December 31, 2019 (dollars in thousands): 2020 $ 10,137 2021 9,169 2022 8,641 2023 7,998 2024 7,119 Thereafter 24,996 Total non-cancelable lease payments $ 68,060
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, 2020 are summarized below. Since commitments associated with letters of credit, unused capacity of Warehouse Purchase Program loans, allowance for credit losses on off-balance sheet credit exposure 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 $ 104,592 $ 10,531 $ 1,619 $ — $ 116,742 Unused capacity on Warehouse Purchase Program loans 858,238 — — — 858,238 Commitments to extend credit 1,854,275 936,045 291,181 1,238,653 4,320,154 Total $ 2,817,105 $ 946,576 $ 292,800 $ 1,238,653 $ 5,295,134

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 Before Tax Amount Tax Effect Net of Tax Amount Before Tax Amount Tax Effect Net of Tax Amount (Dollars in thousands) Other comprehensive (loss) income: Securities available for sale: Change in unrealized gain during period $ (4,183 ) $ 878 $ (3,305 ) $ 503 $ (106 ) $ 397 Total securities available for sale (4,183 ) 878 (3,305 ) 503 (106 ) 397 Total other comprehensive (loss) income $ (4,183 ) $ 878 $ (3,305 ) $ 503 $ (106 ) $ 397
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 (Dollars in thousands) Balance at December 31, 2019 $ 602 $ 602 Other comprehensive loss (3,305 ) (3,305 ) Balance at March 31, 2020 $ (2,703 ) $ (2,703 ) Balance at December 31, 2018 $ 310 $ 310 Other comprehensive income 397 397 Balance at March 31, 2019 $ 707 $ 707

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 and December 31, 2019. March 31, 2020 December 31, 2019 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) Interest rate lock commitments $ 55,892 $ 1,420 $ 3 $ 9,438 $ 305 $ — Forward mortgage-backed securities trades 74,250 — 1,483 40,750 3 83 Commercial loan interest rate swaps and caps: Loan customer counterparty 230,760 14,173 — 231,345 4,829 240 Financial institution counterparty 230,760 — 14,173 231,345 240 4,829
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, 2020 and December 31, 2019 are presented in the following table. Weighted-Average Interest Rate March 31, 2020 December 31, 2019 Received Paid Received Paid Loan customer counterparty 3.18 % 2.36 % 3.42 % 2.86 %
Schedule of Income (Loss) from Derivatives Not Designated as Hedging Instruments	Income (loss) for the three months ended March 31, 2020 and 2019 was as follows: Three Months Ended March 31, Derivatives not designated as hedging instruments 2020 2019 Interest rate lock commitments $ 1,112 $ — Forward mortgage-backed securities trades (1,937 ) —

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Amounts Recorded on Consolidated Balance Sheet on Acquisition Date	The assets and liabilities of LegacyTexas were recorded on the consolidated balance sheet at estimated fair value on the acquisition date. As of March 31, 2020, the following table presents the amounts recorded on the consolidated balance sheet on the acquisition date (dollars in thousands). Initially Recorded at Acquisition Date Measurements Period Adjustments Adjusted Values as of March 31, 2020 Fair value of consideration paid: Common stock issued (26,228,148 shares) $ 1,810,267 $ — $ 1,810,267 Cash 318,018 — 318,018 Total consideration paid $ 2,128,285 $ — $ 2,128,285 Fair value of assets acquired: Cash and due from banks $ 228,649 $ — $ 228,649 Securities held to maturity 472,933 — 472,933 Loans held for sale 60,818 — 60,818 Loans held for investment 6,771,080 — 6,771,080 Loans held for investment - Warehouse Purchase Program 1,693,049 — 1,693,049 Bank premises and equipment 67,347 — 67,347 Other real estate owned 4,876 — 4,876 Core deposit intangibles 60,058 — 60,058 Federal Home Loan Bank stock 117,939 — 117,939 Bank owned life insurance and other assets 242,592 (139 ) 242,453 Total assets acquired 9,719,341 (139 ) 9,719,202 Fair value of liabilities assumed: Deposits 6,434,732 — 6,434,732 Other borrowings 2,078,682 — 2,078,682 Securities sold under repurchase agreements 57,670 — 57,670 Trust preferred securities 15,376 — 15,376 Subordinated notes 125,950 — 125,950 Other liabilities 201,472 (666 ) 200,806 Total liabilities assumed 8,913,882 (666 ) 8,913,216 Fair value of net assets acquired $ 805,459 $ 527 $ 805,986 Goodwill resulting from acquisition $ 1,322,826 $ (527 ) $ 1,322,299
Summary of Pro Forma Information	The following pro forma information presents the results of operations for the three months ended March 31, 2019, as if the Merger had occurred on January 1, 2019 (dollars in thousands, except per share amounts). Three Months Ended March 31, 2019 Net interest income $ 265,247 Net income 95,769 Basic earnings per share 1.00 Diluted earnings per share 1.00

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, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 130,848	$ 82,402
Basic, Weighted average shares outstanding (in shares)	94,371	69,847
Weighted average shares outstanding, per share amount	$ 1.39	$ 1.18
Diluted, Weighted average shares outstanding (in shares)	94,371	69,847
Diluted	$ 1.39	$ 1.18

Income Per Common Share - Addit

Income Per Common Share - Additional Information (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Number of options outstanding	0
Antidilutive Securities excluded from computation of earnings per share, amount	0	0

New Accounting Standards - Addi

New Accounting Standards - Additional Information (Details) - Accounting Standards Update 2016-13 [Member]	3 Months Ended
	Mar. 31, 2020USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Increase in allowance for credit losses for loans	$ 108,700,000
Increase in allowance for credit losses for off-balance sheet credit exposures	24,400,000
Increase in allowance for credit losses for loans	131,800,000
Allowance for credit losses related to debt securities	0
Legacy Texas [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Increase in allowance for credit losses for loans	102,500,000
Increase in allowance for credit losses for off-balance sheet credit exposures	6,300,000
Increase in allowance for credit losses for loans	$ 130,300,000

New Accounting Standards - Sche

New Accounting Standards - Schedule of Impact of Adopting ASU 2016-13 (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	$ 327,206	$ 328,007	$ 87,469	$ 86,091	$ 86,440
Allowance for credit losses on off-balance sheet credit exposure	29,947	29,947	5,599
Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		240,538
Allowance for credit losses on off-balance sheet credit exposure		24,348
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	5,769		2,971	3,284	3,693
Pre-ASC 326 Adoption [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		87,469
Allowance for credit losses on off-balance sheet credit exposure		5,599
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	28,741	28,729	14,654	16,192	15,582
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		14,075
Real Estate [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		5,768
Real Estate [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		2,797
Real Estate [Member] | 1-4 Family [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	23,539	23,544	15,277	14,455	14,135
Real Estate [Member] | 1-4 Family [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		8,267
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	61,403	61,322	12,332	11,590	11,220
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		48,990
Real Estate [Member] | Pre-ASC 326 Adoption [Member] | Construction, Land Development and Other Land Loans [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		14,654
Real Estate [Member] | Pre-ASC 326 Adoption [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		2,971
Real Estate [Member] | Pre-ASC 326 Adoption [Member] | 1-4 Family [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		15,277
Real Estate [Member] | Pre-ASC 326 Adoption [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		12,332
Commercial and Industrial [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	180,097	180,069	40,445	39,059	40,223
Commercial and Industrial [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		139,624
Commercial and Industrial [Member] | Pre-ASC 326 Adoption [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		40,445
Consumer and Other [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans	$ 27,657	28,575	$ 1,790	$ 1,511	$ 1,587
Consumer and Other [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		26,785
Consumer and Other [Member] | Pre-ASC 326 Adoption [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit losses on loans		$ 1,790

Securities - Schedule of Amorti

Securities - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	$ 318,676	$ 286,901
Available for Sale, Gross Unrealized Gains	815	1,350
Available for Sale, Gross Unrealized Losses	(4,236)	(588)
Available for Sale	315,255	287,663
Held to Maturity, Amortized Cost	7,980,240	8,282,393
Held to Maturity, Gross Unrealized Gains	158,268	56,865
Held to Maturity, Gross Unrealized Losses	(2,134)	(35,407)
Held to Maturity	8,136,374	8,303,851
States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	305	470
Available for Sale, Gross Unrealized Gains	1	1
Available for Sale	306	471
Held to Maturity, Amortized Cost	208,744	238,347
Held to Maturity, Gross Unrealized Gains	7,172	7,632
Held to Maturity, Gross Unrealized Losses	(563)	(189)
Held to Maturity	215,353	245,790
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	269,777	235,222
Available for Sale, Gross Unrealized Gains	175	690
Available for Sale, Gross Unrealized Losses	(3,485)	(139)
Available for Sale	266,467	235,773
Held to Maturity, Amortized Cost	184,540	203,470
Held to Maturity, Gross Unrealized Gains	4,156	1,115
Held to Maturity, Gross Unrealized Losses	(39)	(373)
Held to Maturity	188,657	204,212
Mortgage-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Amortized Cost	48,594	51,209
Available for Sale, Gross Unrealized Gains	639	659
Available for Sale, Gross Unrealized Losses	(751)	(449)
Available for Sale	48,482	51,419
Held to Maturity, Amortized Cost	7,579,997	7,826,643
Held to Maturity, Gross Unrealized Gains	146,864	48,060
Held to Maturity, Gross Unrealized Losses	(1,532)	(34,845)
Held to Maturity	7,725,329	7,839,858
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, Amortized Cost	6,959	13,933
Held to Maturity, Gross Unrealized Gains	76	58
Held to Maturity	$ 7,035	$ 13,991

Securities - Additional Informa

Securities - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020USD ($)SegmentSecurity	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)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	2.50%
Securities in Unrealized Loss Positions Qualitative Disclosure Number of Positions Greater Than or Equal to One Year | Security	35		138
Gain (loss) on sale of securities	$ 0	$ 0
Available for sale securities, at fair value	315,255,000		$ 287,663,000
Collateralized Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	5,670,000,000		5,980,000,000
Available for sale securities, at fair value	$ 5,780,000,000		$ 5,990,000,000
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, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	$ 177,852	$ 85,146
Available for Sale, Unrealized Losses, Less than 12 Months	(4,224)	(585)
Available for Sale, Estimated Fair Value, 12 Months or More	1,732	1,828
Available for Sale, Unrealized Losses, 12 Months or More	(12)	(3)
Available for Sale, Estimated Fair Value, Total	179,584	86,974
Available for Sale, Unrealized Losses, Total	(4,236)	(588)
Held to Maturity, Estimated Fair Value, Less than 12 Months	103,135	1,060,533
Held to Maturity, Unrealized Losses, Less than 12 Months	(1,127)	(3,573)
Held to Maturity, Estimated Fair Value, 12 Months or More	210,809	3,114,006
Held to Maturity, Unrealized Losses, 12 Months or More	(1,007)	(31,834)
Held to Maturity, Estimated Fair Value, Total	313,944	4,174,539
Held to Maturity, Unrealized Losses, Total	(2,134)	(35,407)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	145,162	50,245
Available for Sale, Unrealized Losses, Less than 12 Months	(3,473)	(136)
Available for Sale, Estimated Fair Value, 12 Months or More	1,725	1,818
Available for Sale, Unrealized Losses, 12 Months or More	(12)	(3)
Available for Sale, Estimated Fair Value, Total	146,887	52,063
Available for Sale, Unrealized Losses, Total	(3,485)	(139)
Held to Maturity, Estimated Fair Value, Less than 12 Months	9,426	54,890
Held to Maturity, Unrealized Losses, Less than 12 Months	(39)	(373)
Held to Maturity, Estimated Fair Value, Total	9,426	54,890
Held to Maturity, Unrealized Losses, Total	(39)	(373)
Mortgage-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available for Sale, Estimated Fair Value, Less than 12 Months	32,690	34,901
Available for Sale, Unrealized Losses, Less than 12 Months	(751)	(449)
Available for Sale, Estimated Fair Value, 12 Months or More	7	10
Available for Sale, Estimated Fair Value, Total	32,697	34,911
Available for Sale, Unrealized Losses, Total	(751)	(449)
Held to Maturity, Estimated Fair Value, Less than 12 Months	41,092	947,314
Held to Maturity, Unrealized Losses, Less than 12 Months	(525)	(3,017)
Held to Maturity, Estimated Fair Value, 12 Months or More	210,809	3,110,765
Held to Maturity, Unrealized Losses, 12 Months or More	(1,007)	(31,828)
Held to Maturity, Estimated Fair Value, Total	251,901	4,058,079
Held to Maturity, Unrealized Losses, Total	(1,532)	(34,845)
States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Held to Maturity, Estimated Fair Value, Less than 12 Months	52,617	58,329
Held to Maturity, Unrealized Losses, Less than 12 Months	(563)	(183)
Held to Maturity, Estimated Fair Value, 12 Months or More		3,241
Held to Maturity, Unrealized Losses, 12 Months or More		(6)
Held to Maturity, Estimated Fair Value, Total	52,617	61,570
Held to Maturity, Unrealized Losses, Total	$ (563)	$ (189)

Securities - Investment Securit

Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Held to Maturity, amortized cost, due in one year or less	$ 31,833
Held to Maturity, amortized cost, due after one year through five years	119,381
Held to Maturity, amortized cost, due after five years through ten years	57,735
Held to Maturity, amortized cost, due after ten years	6,754
Held to Maturity, amortized cost, subtotal	215,703
Held to Maturity, amortized cost, mortgage-backed securities and collateralized mortgage obligations	7,764,537
Held to Maturity, Amortized Cost	7,980,240	$ 8,282,393
Held to Maturity, fair value, due in one year or less	31,993
Held to Maturity, fair value, due after one year through five years	123,392
Held to Maturity, fair value, due after five years through ten years	60,219
Held to Maturity, fair value, due after ten years	6,784
Held to Maturity, fair value, subtotal	222,388
Held to Maturity, fair value, mortgage-backed securities and collateralized mortgage obligations	7,913,986
Held to Maturity, fair value, total	8,136,374	8,303,851
Available for Sale, amortized cost, due in one year or less	305
Available for Sale, amortized cost, subtotal	305
Available for Sale, amortized cost, mortgage-backed securities and collateralized mortgage obligations	318,371
Available for Sale, Amortized Cost	318,676	286,901
Available for Sale, fair value, due in one year or less	306
Available for Sale, fair value, subtotal	306
Available for Sale, fair value, mortgage-backed securities and collateralized mortgage obligations	314,949
Available for Sale securities, at fair value	$ 315,255	$ 287,663

Loans and Allowance for Credi_3

Loans and Allowance for Credit Losses - Types of Loans in Loan Portfolio (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale		$ 65,035	$ 80,959
Total loans held for investment		17,348,398	17,211,625
Total loans, including Warehouse Purchase Program		19,127,195	18,845,346
Residential Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale		65,035	80,959
Warehouse Purchase Program [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		1,713,762	1,552,762
Total loans, including Warehouse Purchase Program		1,713,762	1,552,762
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		3,218,763	3,205,595
Total loans, including Warehouse Purchase Program		3,218,763	3,205,595
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		2,051,021	2,064,167
Total loans, including Warehouse Purchase Program		2,051,021	2,064,167
Real Estate [Member] | 1-4 Family [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		4,444,106	4,306,452
Total loans, including Warehouse Purchase Program	[1]	4,509,141	4,387,411
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		6,576,213	6,556,285
Total loans, including Warehouse Purchase Program		6,576,213	6,556,285
Real Estate [Member] | Farmland [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		467,372	495,558
Agriculture [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		167,923	185,297
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans held for investment		423,000	398,271
Total loans, including Warehouse Purchase Program		$ 423,000	$ 398,271
[1]	Includes $65.0 million and $81.0 million of residential mortgage loans held for sale at March 31, 2020 and December 31, 2019, respectively.

Loans and Allowance for Credi_4

Loans and Allowance for Credit Losses - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)contract	Mar. 31, 2019USD ($)contract	Jan. 01, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
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	68.30%
Loans and Leases Receivable, Related Parties	$ 4,073			$ 4,152	$ 1,923
Loans held for investment	$ 17,348,398			$ 17,211,625
Financing Receivable Ratio of Nonperforming Loans to All Loans and Other Real Estate	0.35%			0.33%
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 869	$ 602
Loans and leases receivable, nonaccrual loans	58,200	$ 37,500
Financing Receivable, Allowance for Credit Losses on Loans	$ 327,200			$ 87,500
Allowance for Credit Losses as Percentage of Loans	1.71%			0.46%
Allowance for credit losses on off-balance sheet credit exposure	$ 29,947		$ 29,947	$ 5,599
Commitments expected to fund	1,820,000
Nonaccrual loans	$ 58,194			55,243
Troubled debt restructurings, number of loans | contract	1	1
Financing receivable, number of loans with default | contract	0
Financing receivable, modifications, recorded investment		$ 14,800
Troubled debt restructuring, recorded investment at date of restructure		14,783
Loan to be Considered as Payment Default in Period	90 days
Troubled Debt Restructuring [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit losses on off-balance sheet credit exposure	$ 29,900			5,600
Nonaccrual loans	13,000	$ 14,800
Accounting Standards Update 2016-13 [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit losses on off-balance sheet credit exposure			$ 24,348
Accounting Standards Update 2016-13 [Member] | PCD Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
PCD discount reallocated to allowance for credit losses				131,800
Nonperforming Financial Instruments [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 67,200			$ 62,900

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, 2020	Dec. 31, 2019
Receivables [Abstract]
Beginning balance on January 1	$ 4,152	$ 1,923
New loans		1
Transfers		2,500
Repayments	(79)	(272)
Ending balance	$ 4,073	$ 4,152

Loans and Allowance for Credi_6

Loans and Allowance for Credit Losses - Aging Analysis of Past Due Loans (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		$ 150,643	$ 80,887
Nonaccrual loans		58,194	55,243
Current loans		18,918,358	18,709,216
Total loans		19,127,195	18,845,346
Financing Receivables, 30 to 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		147,388	80,446
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		3,255	441
Warehouse Purchase Program Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Current loans		1,713,762	1,552,762
Total loans		1,713,762	1,552,762
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		3,885	466
Nonaccrual loans		28	103
Current loans		631,382	680,286
Total loans		635,295	680,855
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		3,017	466
Agriculture and Agriculture Real Estate (Includes Farmland) [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		868
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		70,850	16,470
Nonaccrual loans		1,125	1,142
Current loans		1,979,046	2,046,555
Total loans		2,051,021	2,064,167
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		70,850	16,470
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]	41,738	44,325
Nonaccrual loans	[1]	26,632	24,413
Current loans	[1]	4,440,771	4,318,673
Total loans	[1]	4,509,141	4,387,411
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]	39,525	43,884
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]	2,213	441
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		15,453	10,669
Nonaccrual loans		14,685	12,714
Current loans		6,546,075	6,532,902
Total loans		6,576,213	6,556,285
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		15,284	10,669
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		169
Commercial and Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		7,655	7,249
Nonaccrual loans		15,720	16,809
Current loans		3,195,388	3,181,537
Total loans		3,218,763	3,205,595
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		7,653	7,249
Commercial and Industrial [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		2
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans past due and still accruing		11,062	1,708
Nonaccrual loans		4	62
Current loans		411,934	396,501
Total loans		423,000	398,271
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		11,059	$ 1,708
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		$ 3
[1]	Includes $65.0 million and $81.0 million of residential mortgage loans held for sale at March 31, 2020 and December 31, 2019, 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, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	$ 65,035	$ 80,959
Residential Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	$ 65,035	$ 80,959

Loans and Allowance for Credi_8

Loans and Allowance for Credit Losses - Nonperforming Assets (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 17,348,398	$ 17,211,625
Other real estate owned		$ 5,452	$ 6,936
Nonperforming assets to total loans and other real estate		0.35%	0.33%
Nonperforming assets to total loans, excluding Warehouse Purchase Program loans, and other real estate		0.39%	0.36%
Nonperforming Financial Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 61,449	$ 55,684
Repossessed assets		278	323
Other real estate owned		5,452	6,936
Total nonperforming assets		67,179	62,943
Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	[1],[2]	58,194	55,243
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		$ 3,255	$ 441
[1]	Includes troubled debt restructurings of $13.0 million and $13.6 million as of March 31, 2020 and December 31, 2019, 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, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		$ 17,348,398,000	$ 17,211,625,000
Nonperforming Financial Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		61,449,000	55,684,000
Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	[1],[2]	58,194,000	55,243,000
Troubled Debt Restructuring [Member] | Nonperforming Financial Loans [Member] | Finance Receivable Nonaccrual Status [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment		13,000,000	13,600,000
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 $13.0 million and $13.6 million as of March 31, 2020 and December 31, 2019, 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, 2020	Dec. 31, 2019
PCD Loans [Member]
Purchased And Non Purchased Credit Impaired Loans [Line Items]
Outstanding balance		$ 355,160	$ 410,785
Discount	[1]	(29,460)	(167,320)	[2]
Recorded investment		325,700	243,465
Recorded investment		325,700	243,465
Non-PCD Loans [Member]
Purchased And Non Purchased Credit Impaired Loans [Line Items]
Outstanding balance		5,744,368	6,102,540
Discount		(87,613)	(110,130)
Recorded investment		5,656,755	5,992,410
Recorded investment		$ 5,656,755	$ 5,992,410
[1]	(1) ASU 2016-13 became effective for the Company on January 1, 2020.
[2]	(2) Includes $131.8 million in PCD loans credit discount.

Loans and Allowance for Cred_11

Loans and Allowance for Credit Losses - Recorded Investment and Outstanding Balance for Purchased Credit Deteriorated Loans and Non Purchased Credit Deteriorated Loans (Parenthetical) (Details) $ in Millions	Dec. 31, 2019USD ($)
PCD Loans [Member]
Purchased And Non Purchased Credit Impaired Loans [Line Items]
PCD loans credit discount	$ 131.8

Loans and Allowance for Cred_12

Loans and Allowance for Credit Losses - Summary of Changes in Accretable Yields of Acquired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
PCD Loans [Member]
Changes In Accretable Yield for PCI And Non PCI Loans [Line Items]
Balance at beginning of period	$ 35,654	$ 1,534
Adjustments	(175)	19
Accretion	(6,019)	(319)
Balance at March 31,	29,460	1,234
Non-PCD Loans [Member]
Changes In Accretable Yield for PCI And Non PCI Loans [Line Items]
Balance at beginning of period	110,130	14,833
Accretion charge-offs	(54)
Accretion	(22,463)	(1,474)
Balance at March 31,	$ 87,613	$ 13,359

Loans and Allowance for Cred_13

Loans and Allowance for Credit Losses - Risk Grade and Category of Loan (Details) $ in Thousands	Mar. 31, 2020USD ($)
Financing Receivable Impaired [Line Items]
2020	$ 2,519,891
2019	3,897,895
2018	2,892,357
2017	2,444,105
2016	1,638,838
Prior	3,324,163
Revolving Loans	2,404,986
Revolving Loans Converted to Term Loans	4,960
Total	19,127,195
PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020	33,952
2019	60,929
2018	15,290
2017	39,384
2016	4,592
Prior	25,126
Revolving Loans	146,427
Total	325,700
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020	35,227
2019	116,809
2018	84,034
2017	65,679
2016	66,886
Prior	153,495
Revolving Loans	112,003
Revolving Loans Converted to Term Loans	1,162
Total	635,295
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020	978
2019	223
Prior	312
Revolving Loans	318
Total	1,831
Warehouse Purchase Program [Member]
Financing Receivable Impaired [Line Items]
2020	1,713,762
Total	1,713,762
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2020	219,444
2019	855,886
2018	471,576
2017	248,629
2016	32,673
Prior	76,658
Revolving Loans	145,531
Revolving Loans Converted to Term Loans	624
Total	2,051,021
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2019	7,875
2018	129
2017	447
Total	8,451
Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020	256,509
2019	1,029,128
2018	727,381
2017	606,648
2016	568,973
Prior	1,164,562
Revolving Loans	153,949
Revolving Loans Converted to Term Loans	1,991
Total	4,509,141
Real Estate [Member] | 1-4 Family [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2016	264
Prior	5,366
Revolving Loans	1,051
Total	6,681
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020	169,963
2019	1,222,303
2018	1,259,760
2017	1,284,780
2016	840,366
Prior	1,659,717
Revolving Loans	139,324
Total	6,576,213
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020	27,593
2019	21,709
2018	5,476
2017	27,168
2016	578
Prior	18,308
Total	100,832
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	97,263
2019	546,360
2018	302,893
2017	166,395
2016	116,490
Prior	249,242
Revolving Loans	1,739,084
Revolving Loans Converted to Term Loans	1,036
Total	3,218,763
Commercial and Industrial [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020	996
2019	22,175
2018	9,685
2017	11,769
2016	3,750
Prior	1,140
Revolving Loans	128,569
Total	178,084
Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020	27,723
2019	127,409
2018	46,713
2017	71,974
2016	13,450
Prior	20,489
Revolving Loans	115,095
Revolving Loans Converted to Term Loans	147
Total	423,000
Consumer and Other [Member] | PCD Loans [Member]
Financing Receivable Impaired [Line Items]
2020	4,385
2019	8,947
Revolving Loans	16,489
Total	29,821
Grade 1 [Member]
Financing Receivable Impaired [Line Items]
2020	16,287
2019	41,430
2018	11,719
2017	4,752
2016	2,834
Prior	48,721
Revolving Loans	33,434
Revolving Loans Converted to Term Loans	35
Total	159,212
Grade 1 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020	167
2019	2,099
2018	298
2017	258
Prior	1
Revolving Loans	9,019
Total	11,842
Grade 1 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
Prior	29
Total	29
Grade 1 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020	100
Revolving Loans	204
Total	304
Grade 1 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
Prior	1,385
Total	1,385
Grade 1 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	9,544
2019	19,031
2018	5,023
2017	1,221
2016	921
Prior	46,114
Revolving Loans	22,818
Revolving Loans Converted to Term Loans	35
Total	104,707
Grade 1 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020	6,476
2019	20,300
2018	6,398
2017	3,273
2016	1,913
Prior	1,192
Revolving Loans	1,393
Total	40,945
Grade 2 [Member]
Financing Receivable Impaired [Line Items]
2020	8,202
2019	13,928
2018	3,322
2017	52,270
2016	3,790
Prior	18,556
Revolving Loans	88,173
Total	188,241
Grade 2 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2018	13
2017	358
2016	8
Prior	1,756
Total	2,135
Grade 2 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2019	1,119
2017	90
2016	135
Prior	362
Total	1,706
Grade 2 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020	292
2019	775
2018	1,018
2017	895
2016	265
Prior	9,918
Revolving Loans	1,136
Total	14,299
Grade 2 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020	5,862
2019	935
2017	7,948
2016	209
Prior	4,986
Total	19,940
Grade 2 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	341
2019	221
2018	1,280
2017	1,697
2016	1,497
Prior	1,534
Revolving Loans	85,570
Total	92,140
Grade 2 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020	1,707
2019	10,878
2018	1,011
2017	41,282
2016	1,676
Revolving Loans	1,467
Total	58,021
Grade 3 [Member]
Financing Receivable Impaired [Line Items]
2020	2,419,170
2019	3,599,846
2018	2,700,110
2017	2,037,870
2016	1,405,338
Prior	2,834,719
Revolving Loans	1,891,563
Revolving Loans Converted to Term Loans	2,763
Total	16,891,379
Grade 3 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020	26,553
2019	100,074
2018	78,662
2017	62,508
2016	59,832
Prior	126,263
Revolving Loans	82,030
Revolving Loans Converted to Term Loans	4
Total	535,926
Grade 3 [Member] | Warehouse Purchase Program [Member]
Financing Receivable Impaired [Line Items]
2020	1,713,762
Total	1,713,762
Grade 3 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2020	215,615
2019	818,291
2018	437,168
2017	125,916
2016	28,173
Prior	64,486
Revolving Loans	132,231
Revolving Loans Converted to Term Loans	624
Total	1,822,504
Grade 3 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020	255,393
2019	1,011,615
2018	715,736
2017	589,506
2016	556,826
Prior	1,097,425
Revolving Loans	146,389
Revolving Loans Converted to Term Loans	1,470
Total	4,374,360
Grade 3 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020	127,368
2019	1,161,018
2018	1,183,252
2017	1,106,578
2016	653,077
Prior	1,362,652
Revolving Loans	120,075
Total	5,714,020
Grade 3 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	66,617
2019	428,024
2018	246,098
2017	125,966
2016	97,689
Prior	164,771
Revolving Loans	1,337,870
Revolving Loans Converted to Term Loans	518
Total	2,467,553
Grade 3 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020	13,862
2019	80,824
2018	39,194
2017	27,396
2016	9,741
Prior	19,122
Revolving Loans	72,968
Revolving Loans Converted to Term Loans	147
Total	263,254
Grade 4 [Member]
Financing Receivable Impaired [Line Items]
2020	38,200
2019	150,126
2018	135,937
2017	291,460
2016	196,736
Prior	346,780
Revolving Loans	203,568
Revolving Loans Converted to Term Loans	2,162
Total	1,364,969
Grade 4 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020	5,561
2019	10,223
2018	4,704
2017	2,555
2016	6,860
Prior	23,985
Revolving Loans	17,707
Revolving Loans Converted to Term Loans	1,158
Total	72,753
Grade 4 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2020	3,829
2019	28,601
2018	31,715
2017	122,176
2016	3,763
Prior	9,340
Revolving Loans	12,566
Total	211,990
Grade 4 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2020	724
2019	14,698
2018	7,402
2017	12,131
2016	10,200
Prior	33,866
Revolving Loans	1,636
Revolving Loans Converted to Term Loans	521
Total	81,178
Grade 4 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2020	9,140
2019	34,890
2018	67,523
2017	129,964
2016	164,600
Prior	246,546
Revolving Loans	17,749
Total	670,412
Grade 4 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	17,653
2019	56,789
2018	24,562
2017	24,629
2016	11,193
Prior	32,869
Revolving Loans	132,853
Revolving Loans Converted to Term Loans	483
Total	301,031
Grade 4 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2020	1,293
2019	4,925
2018	31
2017	5
2016	120
Prior	174
Revolving Loans	21,057
Total	27,605
Grade 5 [Member]
Financing Receivable Impaired [Line Items]
2020	2,724
2019	23,195
2018	8,116
2017	14,450
2016	4,738
Prior	17,949
Revolving Loans	8,944
Total	80,116
Grade 5 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020	637
2019	4,190
2018	329
Prior	990
Revolving Loans	2,929
Total	9,075
Grade 5 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2018	2,564
Prior	363
Total	2,927
Grade 5 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2019	224
2018	2,052
2017	1,282
2016	111
Prior	2,112
Total	5,781
Grade 5 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2018	2,259
2017	12,909
2016	4,251
Prior	14,463
Total	33,882
Grade 5 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	2,087
2019	18,781
2018	840
2017	241
2016	376
Prior	21
Revolving Loans	4,298
Total	26,644
Grade 5 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2018	72
2017	18
Revolving Loans	1,717
Total	1,807
Grade 6 [Member]
Financing Receivable Impaired [Line Items]
2020	1,356
2019	5,889
2018	4,078
2017	529
2016	4,287
Prior	17,486
Revolving Loans	28,532
Total	62,157
Grade 6 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2020	1,331
2016	186
Prior	188
Total	1,705
Grade 6 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
2016	602
Prior	1,688
Total	2,290
Grade 6 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2019	29
2017	333
2016	138
Prior	1,948
Revolving Loans	24
Total	2,472
Grade 6 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2019	3,745
2018	1,250
2017	196
2016	3,239
Prior	11,153
Revolving Loans	1,500
Total	21,083
Grade 6 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2020	25
2019	581
2018	2,828
2016	122
Prior	2,509
Revolving Loans	27,007
Total	33,072
Grade 6 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2019	1,534
Revolving Loans	1
Total	1,535
Grade 7 [Member]
Financing Receivable Impaired [Line Items]
2019	2,552
2018	13,785
2017	3,390
2016	16,500
Prior	14,733
Revolving Loans	4,345
Total	55,305
Grade 7 [Member] | Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
2018	28
Total	28
Grade 7 [Member] | Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
Prior	390
Revolving Loans	734
Total	1,124
Grade 7 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2019	1,787
2018	1,173
2017	2,501
2016	1,159
Prior	13,834
Revolving Loans	3,509
Total	23,963
Grade 7 [Member] | Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
2019	6
2017	17
2016	14,412
Prior	224
Total	14,659
Grade 7 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2019	758
2018	12,577
2017	872
2016	929
Prior	284
Revolving Loans	99
Total	15,519
Grade 7 [Member] | Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
2019	1
2018	7
Prior	1
Revolving Loans	3
Total	12
Grade 8 [Member]
Financing Receivable Impaired [Line Items]
2016	23
Prior	93
Total	116
Grade 8 [Member] | Real Estate [Member] | 1-4 Family [Member]
Financing Receivable Impaired [Line Items]
2016	10
Prior	93
Total	103
Grade 8 [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
2016	13
Total	$ 13

Loans and Allowance for Cred_14

Loans and Allowance for Credit Losses - Risk Grade and Category of Loan (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable Impaired [Line Items]
Loans held for sale	$ 65,035	$ 80,959
Residential Mortgage Loans [Member]
Financing Receivable Impaired [Line Items]
Loans held for sale	$ 65,035	$ 80,959

Loans and Allowance for Cred_15

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, 2020	Mar. 31, 2019
Allowance for credit losses:
Allowance for credit losses, beginning balance	$ 87,469	$ 86,440
Provision for credit losses		700
Charge-offs	(1,987)	(2,909)
Recoveries	1,186	1,860
Net charge-offs	(801)	(1,049)
Allowance for credit losses, ending balance	327,206	86,091
Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	240,538
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	2,971	3,693
Provision for credit losses		(1,687)
Charge-offs	(31)	(10)
Recoveries	32	1,288
Net charge-offs	1	1,278
Allowance for credit losses, ending balance	5,769	3,284
Agriculture and Agriculture Real Estate (Includes Farmland) [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	2,797
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	14,654	15,582
Provision for credit losses		610
Charge-offs		(44)
Recoveries	12	44
Net charge-offs	12
Allowance for credit losses, ending balance	28,741	16,192
Real Estate [Member] | Construction, Land Development and Other Land Loans [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	14,075
Real Estate [Member] | 1-4 Family [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	15,277	14,135
Provision for credit losses		317
Charge-offs	(29)	(6)
Recoveries	24	9
Net charge-offs	(5)	3
Allowance for credit losses, ending balance	23,539	14,455
Real Estate [Member] | 1-4 Family [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	8,267
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	12,332	11,220
Provision for credit losses		369
Recoveries	81	1
Net charge-offs	81	1
Allowance for credit losses, ending balance	61,403	11,590
Real Estate [Member] | Commercial Real Estate (Includes Multi-Family Residential) [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	48,990
Commercial and Industrial [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	40,445	40,223
Provision for credit losses		555
Charge-offs	(611)	(1,957)
Recoveries	639	238
Net charge-offs	28	(1,719)
Allowance for credit losses, ending balance	180,097	39,059
Commercial and Industrial [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	139,624
Consumer and Other [Member]
Allowance for credit losses:
Allowance for credit losses, beginning balance	1,790	1,587
Provision for credit losses		536
Charge-offs	(1,316)	(892)
Recoveries	398	280
Net charge-offs	(918)	(612)
Allowance for credit losses, ending balance	27,657	$ 1,511
Consumer and Other [Member] | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses:
Impact of adoption ASC 326	$ 26,785

Loans and Allowance for Cred_16

Loans and Allowance for Credit Losses - Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020contract	Mar. 31, 2019USD ($)contract
Financing Receivable Modifications [Line Items]
Troubled debt restructurings, number of loans | contract	1	1
Troubled debt restructurings, pre-modification outstanding recorded investment		$ 14,783
Troubled debt restructurings, post-modification outstanding recorded investment		$ 14,783
Commercial and Industrial [Member]
Financing Receivable Modifications [Line Items]
Troubled debt restructurings, number of loans | contract		1
Troubled debt restructurings, pre-modification outstanding recorded investment		$ 14,783
Troubled debt restructurings, post-modification outstanding recorded investment		$ 14,783

Fair Value - Fair Value Assets

Fair Value - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available for sale securities:
Available for sale securities, at fair value	$ 315,255	$ 287,663
Fair Value, Measurements, Recurring [Member]
Available for sale securities:
Available for sale securities, at fair value	315,255	287,663
Fair Value, Measurements, Recurring [Member] | Loan Customer Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value	14,173	4,829
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value		240
Fair Value, Measurements, Recurring [Member] | Financial Institution Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value		240
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	14,173	4,829
Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value	1,420	305
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	3
Fair Value, Measurements, Recurring [Member] | Forward Mortgage-Backed Securities Trades [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value		3
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	1,483	83
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	315,255	287,663
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Loan Customer Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value	14,173	4,829
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value		240
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Financial Institution Counterparty [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value		240
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	14,173	4,829
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest Rate Lock Commitments [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value	1,420	305
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	3
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Forward Mortgage-Backed Securities Trades [Member]
Derivative financial instruments:
Derivative financial instruments, assets at fair value		3
Derivative financial instruments:
Derivative financial instruments, liabilities at fair value	1,483	83
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member]
Available for sale securities:
Available for sale securities, at fair value	306	471
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	306	471
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations [Member]
Available for sale securities:
Available for sale securities, at fair value	266,467	235,773
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	266,467	235,773
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities [Member]
Available for sale securities:
Available for sale securities, at fair value	48,482	51,419
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities [Member] | Level 2 [Member]
Available for sale securities:
Available for sale securities, at fair value	$ 48,482	$ 51,419

Fair Value - Additional Informa

Fair Value - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Fair Value Disclosures [Abstract]
Other real estate, additions	$ 112
Real estate owned outstanding	92
Additions to impaired loans	$ 11,500

Fair Value - Summary of Carryin

Fair Value - Summary of Carrying and Fair Value Information of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Cash and due from banks	$ 381,458	$ 573,589
Federal funds sold	676	519
Held to maturity securities	8,136,374	8,303,851
Loans held for sale	65,035	80,959
Loans held for investment	17,348,398	17,211,625
Other real estate owned	5,452	6,936
Liabilities
Noninterest-bearing	7,461,323	7,763,894
Interest-bearing	16,365,034	16,435,838
Other borrowings	1,338,429	1,303,730
Securities sold under repurchase agreements	344,695	377,294
Subordinated notes	125,585	125,804
Carrying Amount [Member]
Assets
Cash and due from banks	381,458	573,589
Federal funds sold	676	519
Held to maturity securities	7,980,240	8,282,393
Loans held for sale	65,035	80,959
Loans held for investment, net of allowance	17,021,192	17,124,156
Other real estate owned	5,452	6,936
Liabilities
Noninterest-bearing	7,461,323	7,763,894
Interest-bearing	16,365,034	16,435,838
Other borrowings	1,338,429	1,303,730
Securities sold under repurchase agreements	344,695	377,294
Subordinated notes	125,585	125,804
Carrying Amount [Member] | Warehouse Purchase Program [Member]
Assets
Loans held for investment	1,713,762	1,552,762
Estimated Fair Value [Member]
Assets
Cash and due from banks	381,458	573,589
Federal funds sold	676	519
Held to maturity securities	8,136,374	8,303,851
Loans held for sale	65,035	80,959
Loans held for investment, net of allowance	16,714,427	17,045,523
Other real estate owned	5,452	6,936
Liabilities
Noninterest-bearing	7,461,323	7,763,894
Interest-bearing	16,396,178	16,437,453
Other borrowings	1,338,686	1,303,941
Securities sold under repurchase agreements	344,739	377,302
Subordinated notes	125,732	125,743
Estimated Fair Value [Member] | Level 1 [Member]
Assets
Cash and due from banks	381,458	573,589
Federal funds sold	676	519
Estimated Fair Value [Member] | Level 2 [Member]
Assets
Held to maturity securities	8,136,374	8,303,851
Loans held for sale	65,035	80,959
Other real estate owned	5,452	6,936
Liabilities
Noninterest-bearing	7,461,323	7,763,894
Interest-bearing	16,396,178	16,437,453
Other borrowings	1,338,686	1,303,941
Securities sold under repurchase agreements	344,739	377,302
Subordinated notes	125,732	125,743
Estimated Fair Value [Member] | Level 3 [Member]
Assets
Loans held for investment, net of allowance	16,714,427	17,045,523
Estimated Fair Value [Member] | Warehouse Purchase Program [Member]
Assets
Loans held for investment	1,713,762	1,552,762
Estimated Fair Value [Member] | Warehouse Purchase Program [Member] | Level 2 [Member]
Assets
Loans held for investment	$ 1,713,762	$ 1,552,762

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, 2020	Mar. 31, 2019	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill, Beginning balance	$ 3,223,671	$ 1,900,845	$ 1,900,845
Goodwill, LegacyTexas Merger			1,322,826
Goodwill, Ending balance	3,223,144		3,223,671
Goodwill, Measurement period adjustment of LegacyTexas Merger	(527)
Core Deposit Intangibles, Beginning balance	86,404	32,883	32,883
Core Deposit Intangibles, Amortization	(3,363)	$ (1,319)	(6,537)
Core Deposit Intangibles, LegacyTexas Merger			60,058
Core Deposit Intangibles, Ending balance	$ 83,041		$ 86,404

Goodwill and Core Deposit Int_4

Goodwill and Core Deposit Intangibles - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Schedule Of Intangible Assets And Goodwill [Line Items]
Impairment recorded on goodwill and core deposit intangibles	$ 0
Amortization expense related to intangible assets	$ 3,363,000	$ 1,319,000	$ 6,537,000
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, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Remaining 2020	$ 9,806
2021	11,551
2022	10,336
2023	9,360
2024	8,699
Thereafter	33,289
Total	$ 83,041	$ 86,404	$ 32,883

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)Planshares	Mar. 31, 2019USD ($)	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 | $	$ 14.8
Weighted-average period of cost expected to be recognized	1 year 6 months 14 days
Number of shares outstanding	0
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense | $	$ 3.3	$ 2.8
2020 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares authorized for issuance	2,500,000
2012 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares authorized for issuance			1,250,000
Shares issued	357,013
Number of restricted shares granted	506,362

Contractual Obligations and O_3

Contractual Obligations and Off-Balance Sheet Items - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020	Dec. 31, 2019
Contractual Obligations And Off Balance Sheet Items [Line Items]
Operating lease, right-of-use asset	$ 54,000
Operating lease, liability	$ 54,000
Operating lease, weighted average remaining lease term	8 years
Operating lease, weighted average discount rate, percent	2.49%
Operating lease, payments	$ 3,600	$ 1,400
Right-of-Use asset obtained in exchange for operating lease liability	1,500
Allowance for credit losses on off-balance sheet credit exposure	$ 29,947		$ 29,947	$ 5,599
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
Subordinated Notes Payable [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
Interest payable	$ 40,300
Federal Home Loan Bank Advance And Notes Payable [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
Interest payable	$ 299

Contractual Obligations and O_4

Contractual Obligations and Off-Balance Sheet Items - Contractual Obligations and Other Commitments (Details) - Lease Total [Member] $ in Thousands	Mar. 31, 2020USD ($)
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	$ 1,343,112
More than 1 year but less than 3 years	15,392
3 years or more but less than 5 years	14,346
5 years or more	130,987
Total	1,503,837
Subordinated Notes Payable [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	6,875
More than 1 year but less than 3 years	13,750
3 years or more but less than 5 years	13,750
5 years or more	130,958
Total	165,333
Federal Home Loan Bank Advance And Notes Payable [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	1,336,237
More than 1 year but less than 3 years	1,642
3 years or more but less than 5 years	596
5 years or more	29
Total	$ 1,338,504

Contractual Obligations and O_5

Contractual Obligations and Off-Balance Sheet Items - Future Undiscounted Cash Payments Associated with its Operating Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Remaining 2020	$ 7,660
2021	9,523	$ 9,169
2022	8,998	8,641
2023	8,250	7,998
2024	7,369	7,119
2025	6,978
Thereafter	18,247
Total undiscounted lease payments	$ 67,025	$ 68,060

Contractual Obligations and O_6

Contractual Obligations and Off-Balance Sheet Items - Summary of Non-Cancelable Future Operating Lease Commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2020		$ 10,137
2021	$ 9,523	9,169
2022	8,998	8,641
2023	8,250	7,998
2024	7,369	7,119
Thereafter		24,996
Total undiscounted lease payments	$ 67,025	$ 68,060

Contractual Obligations and O_7

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, 2020USD ($)
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	$ 2,817,105
More than 1 year but less than 3 years	946,576
3 years or more but less than 5 years	292,800
5 years or more	1,238,653
Total	5,295,134
Unused capacity on Warehouse Purchase Program loans [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	858,238
Total	858,238
Commitments to Extend Credit [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	1,854,275
More than 1 year but less than 3 years	936,045
3 years or more but less than 5 years	291,181
5 years or more	1,238,653
Total	4,320,154
Standby Letters of Credit [Member]
Contractual Obligations And Off Balance Sheet Items [Line Items]
1 year or less	104,592
More than 1 year but less than 3 years	10,531
3 years or more but less than 5 years	1,619
5 years or more	0
Total	$ 116,742

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, 2020	Mar. 31, 2019
Equity [Abstract]
Change in unrealized gain during period, before tax amount	$ (4,183)	$ 503
Change in unrealized gain during period, tax effect	878	(106)
Change in unrealized gain during period, net of tax amount	(3,305)	397
Total securities available for sale, before tax amount	(4,183)	503
Total securities available for sale, tax effect	878	(106)
Total securities available for sale, net of tax amount	(3,305)	397
Total other comprehensive (loss) income, before tax amount	(4,183)	503
Total other comprehensive (loss) income, tax effect	878	(106)
Other comprehensive (loss) income, net of tax	$ (3,305)	$ 397

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, 2020	Mar. 31, 2019
Beginning balance, accumulated other comprehensive income	$ 602	$ 310
Other comprehensive income (loss)	(3,305)	397
Ending balance, accumulated other comprehensive income	(2,703)	707
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance, accumulated other comprehensive income	602	310
Other comprehensive income (loss)	(3,305)	397
Ending balance, accumulated other comprehensive income	$ (2,703)	$ 707

Derivative Financial Instrume_3

Derivative Financial Instruments - Schedule of Notional Balances and Fair Value of Derivative Positions (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Interest Rate Lock Commitments [Member]
Derivatives Fair Value [Line Items]
Outstanding Notional Balance	$ 55,892	$ 9,438
Derivative financial instruments, assets at fair value	1,420	305
Derivative financial instruments, liabilities at fair value	3
Forward Mortgage-Backed Securities Trades [Member]
Derivatives Fair Value [Line Items]
Outstanding Notional Balance	74,250	40,750
Derivative financial instruments, assets at fair value		3
Derivative financial instruments, liabilities at fair value	1,483	83
Commercial Loan Interest Rate Swaps and Caps [Member] | Loan Customer Counterparty [Member]
Derivatives Fair Value [Line Items]
Outstanding Notional Balance	230,760	231,345
Derivative financial instruments, assets at fair value	14,173	4,829
Derivative financial instruments, liabilities at fair value		240
Commercial Loan Interest Rate Swaps and Caps [Member] | Financial Institution Counterparty [Member]
Derivatives Fair Value [Line Items]
Outstanding Notional Balance	230,760	231,345
Derivative financial instruments, assets at fair value		240
Derivative financial instruments, liabilities at fair value	$ 14,173	$ 4,829

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, 2020	Dec. 31, 2019
Derivative [Line Items]
Weighted-Average Interest Rate Received	0.0318	0.0342
Weighted-Average Interest Rate Paid	0.0236	0.0286

Derivative Financial Instrume_5

Derivative Financial Instruments - Additional Information (Details) - Interest Rate Swap - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Credit exposure	$ 14,200,000	$ 4,800,000
Cash collateral pledged	14,300,000	$ 9,300,000
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)

Acquisitions (Summary) - Additi

Acquisitions (Summary) - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020
Minimum [Member]
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	10 years
Maximum [Member]
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	15 years

Acquisitions (2019 Acquisitions

Acquisitions (2019 Acquisitions) - Additional Information (Details) $ / shares in Units, $ in Thousands	Nov. 01, 2019USD ($)LocationCity$ / sharesshares	Mar. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Total assets		$ 31,743,499	$ 32,185,708
Total deposits		23,826,357	24,199,732
Shareholders’ equity		5,855,574	5,970,835		$ 4,109,790	$ 4,052,824
Goodwill		3,223,144	3,223,671			$ 1,900,845
Finite-lived intangible assets acquired			60,058
Merger-related expenses		$ 544
Legacy Texas [Member]
Business Acquisition [Line Items]
Total assets				$ 10,500,000
Total gross loans				9,100,000
Total deposits				6,500,000
Shareholders’ equity				$ 1,200,000
Legacy Texas [Member]
Business Acquisition [Line Items]
Business acquisition, equity interest issued or issuable, number of shares | shares	26,228,148	26,228,148
Business acquisition, closing share price | $ / shares	$ 69.02
Payments to acquire businesses in cash	$ 318,000	$ 318,018
Payments to acquire businesses in cash, cash	308,600
Payments to acquire businesses in cash, cash for taxes withheld	$ 9,400
Goodwill		1,322,299
Finite-lived intangible assets acquired		56,400
Merger-related expenses		544	46,400
Revenue, actual		$ 106,200	$ 79,700
Legacy Texas [Member] | North Texas [Member]
Business Acquisition [Line Items]
Number of bank operating locations | Location	42
Number of bank operating cities | City	19

Acquisitions - Amounts Recorded

Acquisitions - Amounts Recorded on Consolidated Balance Sheet on Acquisition Date (Details) - USD ($) $ in Thousands	Nov. 01, 2019	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair value of liabilities assumed:
Goodwill		$ 3,223,144	$ 3,223,671	$ 1,900,845
Legacy Texas [Member]
Fair value of consideration paid:
Common stock issued (26,228,148 shares)		1,810,267
Payments to acquire businesses in cash	$ 318,000	318,018
Total consideration paid		2,128,285
Fair value of assets acquired:
Cash and due from banks		228,649
Securities held to maturity		472,933
Loans held for sale		60,818
Loans held for investment		6,771,080
Loans held for investment - Warehouse Purchase Program		1,693,049
Bank premises and equipment		67,347
Other real estate owned		4,876
Core deposit intangibles		60,058
Federal Home Loan Bank stock		117,939
Bank owned life insurance and other assets		242,453
Total assets acquired		9,719,202
Fair value of liabilities assumed:
Deposits		6,434,732
Other borrowings		2,078,682
Securities sold under repurchase agreements		57,670
Trust preferred securities		15,376
Subordinated notes		125,950
Other liabilities		200,806
Total liabilities assumed		8,913,216
Fair value of net assets acquired		805,986
Goodwill		1,322,299
ASC 805 [Member] | Legacy Texas [Member]
Fair value of consideration paid:
Common stock issued (26,228,148 shares)	1,810,267
Payments to acquire businesses in cash	318,018
Total consideration paid	2,128,285
Fair value of assets acquired:
Cash and due from banks	228,649
Securities held to maturity	472,933
Loans held for sale	60,818
Loans held for investment	6,771,080
Loans held for investment - Warehouse Purchase Program	1,693,049
Bank premises and equipment	67,347
Other real estate owned	4,876
Core deposit intangibles	60,058
Federal Home Loan Bank stock	117,939
Bank owned life insurance and other assets	242,592
Total assets acquired	9,719,341
Fair value of liabilities assumed:
Deposits	6,434,732
Other borrowings	2,078,682
Securities sold under repurchase agreements	57,670
Trust preferred securities	15,376
Subordinated notes	125,950
Other liabilities	201,472
Total liabilities assumed	8,913,882
Fair value of net assets acquired	805,459
Goodwill	$ 1,322,826
Measurements Period Adjustments [Member] | ASC 805 [Member] | Legacy Texas [Member]
Fair value of assets acquired:
Bank owned life insurance and other assets		(139)
Total assets acquired		(139)
Fair value of liabilities assumed:
Other liabilities		(666)
Total liabilities assumed		(666)
Fair value of net assets acquired		527
Goodwill		$ (527)

Acquisitions - Amounts Record_2

Acquisitions - Amounts Recorded on Consolidated Balance Sheet on Acquisition Date (Parenthetical) (Details) - shares	Nov. 01, 2019	Mar. 31, 2020
Legacy Texas [Member]
Business Acquisition [Line Items]
Business acquisition, equity interest issued or issuable, number of shares	26,228,148	26,228,148

Acquisitions - Summary of Pro F

Acquisitions - Summary of Pro Forma Information (Details) - Legacy Texas [Member] $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)$ / shares
Changes In Accretable Yield for PCI And Non PCI Loans [Line Items]
Net interest income | $	$ 265,247
Net income | $	$ 95,769
Basic earnings per share | $ / shares	$ 1
Diluted earnings per share | $ / shares	$ 1

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - C A R E S Act - Paycheck Protection Program [Member] $ in Billions	May 06, 2020USD ($)Loan	Mar. 31, 2020
Subsequent Event [Line Items]
Term period of loans		2 years
Earned interest rate of term period loans		1.00%
Minimum [Member]
Subsequent Event [Line Items]
Percentage of tiered schedule of loan balance for per loan processing fee		5.00%
Maximum [Member]
Subsequent Event [Line Items]
Percentage of tiered schedule of loan balance for per loan processing fee		1.00%
Subsequent Event
Subsequent Event [Line Items]
Number of loans for small business administration approvals | Loan	10,735
Funded amount | $	$ 1.4