Simmons First National (SFNC) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Entity File Number	000-06253
Document Transition Report	false
Entity Registrant Name	SIMMONS FIRST NATIONAL CORP
Entity Incorporation, State or Country Code	AR
Entity Tax Identification Number	71-0407808
Entity Address, Address Line One	501 Main Street
Entity Address, City or Town	Pine Bluff
Entity Address, State or Province	AR
Entity Address, Postal Zip Code	71601
City Area Code	870
Local Phone Number	541-1000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	SFNC
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		108,968,998
Entity Central Index Key	0000090498
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Mar. 31, 2020	Dec. 31, 2019
ASSETS
Cash and non-interest bearing balances due from banks	$ 244,123,000	$ 277,208,000
Interest bearing balances due from banks and federal funds sold	1,493,076,000	719,415,000
Cash and cash equivalents	1,737,199,000	996,623,000
Interest bearing balances due from banks - time	4,309,000	4,554,000
Held-to-maturity, net of allowance for credit losses of $409 at March 31, 2020	53,968,000	40,927,000
Investment securities:
Available-for-sale securities	2,466,640,000	3,288,343,000
Total investments	2,520,608,000	3,329,270,000
Mortgage loans held for sale	49,984,000	58,102,000
Other assets held for sale	115,315,000	260,332,000
Loans	14,374,277,000	14,425,704,000
Allowance for credit losses on loans	(243,195,000)
Allowance for credit losses on loans		(68,244,000)
Net loans	14,131,082,000	14,357,460,000
Premises and equipment	484,990,000	492,384,000
Foreclosed assets and other real estate owned	20,805,000	19,121,000
Interest receivable	57,039,000	62,707,000
Bank owned life insurance	255,197,000	254,152,000
Goodwill	1,064,978,000	1,055,520,000
Other intangible assets	121,673,000	127,340,000
Other assets	278,173,000	241,578,000
Total assets	20,841,352,000	21,259,143,000
Deposits:
Non-interest bearing transaction accounts	3,572,244,000	3,741,093,000
Interest bearing transaction accounts and savings deposits	8,840,678,000	9,090,878,000
Time deposits	3,146,811,000	3,276,969,000
Total deposits	15,559,733,000	16,108,940,000
Federal funds purchased and securities sold under agreements to repurchase	377,859,000	150,145,000
Other borrowings	1,396,829,000	1,297,599,000
Subordinated debentures	388,396,000	388,260,000
Other liabilities held for sale	58,405,000	159,853,000
Accrued interest and other liabilities	214,730,000	165,422,000
Total liabilities	17,995,952,000	18,270,219,000
Stockholders’ equity:
Preferred stock, 40,040,000 shares authorized; Series D, $0.01 par value, $1,000 liquidation value per share; 767 shares issued and outstanding at March 31, 2020 and December 31, 2019	767,000	767,000
Common stock, Class A, $0.01 par value; 175,000,000 shares authorized at March 31, 2020 and December 31, 2019; 108,966,331 and 113,628,601 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	1,090,000	1,136,000
Surplus	2,026,420,000	2,117,282,000
Undivided profits	778,893,000	848,848,000
Accumulated other comprehensive income	38,230,000	20,891,000
Total stockholders’ equity	2,845,400,000	2,988,924,000
Total liabilities and stockholders’ equity	$ 20,841,352,000	$ 21,259,143,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for credit losses on HTM	$ 409	$ 0
Available-for-sale, allowance for credit loss	269	0
Amortized Cost	$ 2,418,498	$ 3,263,151
Preferred stock, Series D, shares authorized (in shares)	40,040,000	40,040,000
Preferred stock, Series D, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, Series D, liquidation value (in dollars per share)	$ 1,000	$ 1,000
Preferred stock, Series D, shares issued (in shares)	767	767
Preferred stock, Series D, shares outstanding (in shares)	767	767
Common stock, Class A, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, Class A, shares authorized (in shares)	175,000,000	175,000,000
Common stock, Class A, shares issued (in shares)	108,966,331	113,628,601
Common stock, Class A, shares outstanding (in shares)	108,966,331	113,628,601

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
INTEREST INCOME
Loans	$ 187,566	$ 159,440
Interest bearing balances due from banks and federal funds sold	2,441	2,154
Investment securities	18,943	16,281
Mortgage loans held for sale	281	210
TOTAL INTEREST INCOME	209,231	178,085
INTEREST EXPENSE
Deposits	31,277	30,750
Federal funds purchased and securities sold under agreements to repurchase	759	136
Other borrowings	4,877	6,793
Subordinated notes and debentures	4,835	4,411
TOTAL INTEREST EXPENSE	41,748	42,090
NET INTEREST INCOME	167,483	135,995
Provision for credit loss expense	26,134	9,285
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	141,349	126,710
NON-INTEREST INCOME
Investment banking income	877	618
Bank owned life insurance income	1,298	795
Gain on sale of securities, net	32,095	2,740
Other income	12,801	4,156
TOTAL NON-INTEREST INCOME	82,394	34,792
NON-INTEREST EXPENSE
Salaries and employee benefits	67,924	56,367
Occupancy expense, net	9,510	7,475
Furniture and equipment expense	5,723	3,358
Other real estate and foreclosure expense	325	637
Deposit insurance	2,475	2,040
Merger related costs	1,068	1,470
Other operating expenses	38,788	30,062
TOTAL NON-INTEREST EXPENSE	125,813	101,409
INCOME BEFORE INCOME TAXES	97,930	60,093
Provision for income taxes	20,694	12,398
NET INCOME	77,236	47,695
Preferred stock dividends	13	0
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 77,223	$ 47,695
BASIC EARNINGS PER SHARE (in dollars per share)	$ 0.68	$ 0.52
DILUTED EARNINGS PER SHARE (in dollars per share)	$ 0.68	$ 0.51
Trust income
NON-INTEREST INCOME
Non-interest income	$ 7,151	$ 5,708
Service charges on deposit accounts
NON-INTEREST INCOME
Non-interest income	13,328	10,068
Other service charges and fees
NON-INTEREST INCOME
Non-interest income	1,588	1,289
Mortgage lending income
NON-INTEREST INCOME
Non-interest income	5,046	2,823
SBA lending income
NON-INTEREST INCOME
Non-interest income	296	497
Debit and credit card fees
NON-INTEREST INCOME
Non-interest income	$ 7,914	$ 6,098

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 77,236	$ 47,695
OTHER COMPREHENSIVE INCOME (LOSS)
Unrealized holding gains arising during the period on available-for-sale securities	55,569	29,130
Unrealized holding gain on the transfer of held-to-maturity securities to available-for-sale per ASU 2017-12	0	2,547
Less: Reclassification adjustment for realized gains included in net income	32,095	2,740
Other comprehensive income (loss), before tax effect	23,474	28,937
Less: Tax effect of other comprehensive income (loss)	6,135	7,563
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	17,339	21,374
COMPREHENSIVE INCOME	$ 94,575	$ 69,069

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES
Net income	$ 77,236	$ 47,695
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	11,843	7,451
Provision for credit loss expense	26,134	9,285
(Benefit) provision for credit losses on unfunded commitments	(3,000)	300
Gain on sale of investments	(32,095)	(2,740)
Net accretion of investment securities and assets	(14,975)	(9,559)
Net amortization on borrowings	136	91
Stock-based compensation expense	4,506	3,084
Gain on sale of foreclosed assets held for sale	(520)	(32)
Gain on sale of mortgage loans held for sale	(5,843)	(3,342)
Gain on sale of other intangibles	(301)	0
Gain on sale of branches	(5,889)	0
Deferred income taxes	(1,586)	2,081
Income from bank owned life insurance	(1,800)	(876)
Originations of mortgage loans held for sale	(182,550)	(98,255)
Proceeds from sale of mortgage loans held for sale	196,511	109,916
Changes in assets and liabilities:
Interest receivable	5,058	(1,858)
Lease right-of-use assets	2,330	2,294
Other assets	1,325	10,982
Accrued interest and other liabilities	48,313	30,505
Income taxes payable	(21,221)	(10,977)
Net cash provided by operating activities	103,612	96,045
INVESTING ACTIVITIES
Net originations of loans	(49,104)	(18,116)
Decrease in due from banks - time	245	250
Purchases of premises and equipment, net	(10,570)	(13,027)
Proceeds from sale of foreclosed assets held for sale	2,464	7,214
Proceeds from sale of available-for-sale securities	1,076,858	201,516
Proceeds from maturities of available-for-sale securities	1,255,991	56,438
Purchases of available-for-sale securities	(1,458,730)	(110,201)
Proceeds from maturities of held-to-maturity securities	3,561	11,408
Purchases of held-to-maturity securities	(16,997)	0
Proceeds from bank owned life insurance death benefits	763	1,310
Disposition of assets and liabilities held for sale	123,610	1,393
Net cash provided by investing activities	928,091	138,185
FINANCING ACTIVITIES
Net change in deposits	(503,567)	(409,221)
Dividends paid on preferred stock	(13)	0
Dividends paid on common stock	(19,077)	(14,807)
Net change in other borrowed funds	99,230	(175,461)
Net change in federal funds purchased and securities sold under agreements to repurchase	227,714	24,421
Net shares cancelled under stock compensation plans	(3,063)	(2,771)
Shares issued under employee stock purchase plan	956	1,312
Repurchases of common stock	(93,307)	0
Net cash used in financing activities	(291,127)	(576,527)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	740,576	(342,297)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	996,623	833,458
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 1,737,199	$ 491,161

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Surplus	Accumulated Other Comprehensive Income (Loss)	Undivided Profits	Impact of adoption of 2016-13	Impact of adoption of 2016-13Undivided Profits
Balance at Dec. 31, 2018	$ 2,246,434	$ 0	$ 923	$ 1,597,944	$ (27,374)	$ 674,941
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	69,069				21,374	47,695
Stock issued for employee stock purchase plan	1,312		1	1,311
Stock-based compensation plans, net	313		2	311
Dividends on common stock	(14,807)					(14,807)
Balance at Mar. 31, 2019	2,302,321	0	926	1,599,566	(6,000)	707,829
Balance at Dec. 31, 2019	2,988,924	767	1,136	2,117,282	20,891	848,848	$ (128,101)	$ (128,101)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	94,575				17,339	77,236
Stock issued for employee stock purchase plan	956		1	955
Stock-based compensation plans, net	1,443		2	1,441
Stock repurchases – 4,922,336 shares	(93,307)		(49)	(93,258)
Dividends on preferred stock	(13)					(13)
Dividends on common stock	(19,077)					(19,077)
Balance at Mar. 31, 2020	$ 2,845,400	$ 767	$ 1,090	$ 2,026,420	$ 38,230	$ 778,893

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Stock issued for employee stock purchase plan, shares (in shares)	43,681	60,413
Stock issued for compensation plans, shares (in shares)	216,385	160,305
Stock repurchased (in shares)	4,922,336
Cash dividends per share (in dollars per share)	$ 0.17	$ 0.16

Preparation of Interim Financia

Preparation of Interim Financial Statements	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Preparation of Interim Financial Statements	PREPARATION OF INTERIM FINANCIAL STATEMENTS Description of Business and Organizational Structure Simmons First National Corporation (“Company”) is a financial holding company headquartered in Pine Bluff, Arkansas, and the parent company of Simmons Bank, an Arkansas state-chartered bank that has been in operation since 1903. Simmons First Insurance Services, Inc. and Simmons First Insurance Services of TN, LLC are wholly-owned subsidiaries of Simmons Bank and are insurance agencies that offer various lines of personal and corporate insurance coverage to individual and commercial customers. The Company, through its subsidiaries, offers, among other things, consumer, real estate and commercial loans; checking, savings and time deposits; and specialized products and services (such as credit cards, trust and fiduciary services, investments, agricultural finance lending, equipment lending, insurance and small business administration (“SBA”) lending) from approximately 240 financial centers located throughout market areas in Arkansas, Colorado, Illinois, Kansas, Missouri, Oklahoma, Tennessee and Texas. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared based upon Securities and Exchange Commission (“SEC”) rules that permit reduced disclosures for interim periods. Certain information and footnote disclosures have been condensed or omitted in accordance with those rules and regulations. The accompanying consolidated balance sheet as of December 31, 2019 , was derived from audited financial statements. In the opinion of management, these financial statements reflect all adjustments that are necessary for a fair presentation of interim results of operations, including normal recurring accruals. Significant intercompany accounts and transactions have been eliminated in consolidation. The results for the interim periods are not necessarily indicative of results for the full year. For a more complete discussion of significant accounting policies and certain other information, this report should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 , which was filed with the SEC on February 27, 2020 . The preparation of financial statements, in accordance with accounting principles generally accepted in the United States (“US GAAP”), requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, income items and expenses and disclosure of contingent assets and liabilities. The estimates and assumptions used in the accompanying consolidated financial statements are based upon management’s evaluation of the relevant facts and circumstances as of the date of the consolidated financial statements and actual results may differ from these estimates. Such estimates include, but are not limited to, the Company’s allowance for credit losses. Certain prior year amounts have been reclassified to conform to the current year financial statement presentation. These changes and reclassifications did not impact previously reported net income or comprehensive income. Recently Adopted Accounting Standards Fair Value Measurement Disclosures – In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), that eliminates, amends and adds disclosure requirements for fair value measurements. These amendments are part of FASB’s disclosure review project and they are expected to reduce costs for preparers while providing more decision-useful information for financial statement users. The eliminated disclosure requirements include the 1) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; 2) the policy of timing of transfers between levels of the fair value hierarchy; and 3) the valuation processes for Level 3 fair value measurements. Among other modifications, the amended disclosure requirements remove the term “at a minimum” from the phrase “an entity shall disclose at a minimum” to promote the appropriate exercise of discretion by entities and clarifies that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Under the new disclosure requirements, entities must disclose the changes in unrealized gains or losses included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. ASU 2018-13 did not have a material impact on the Company’s fair value disclosures. Credit Losses on Financial Instruments – In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which requires earlier measurement of credit losses, expands the range of information considered in determining expected credit losses and enhances disclosures. The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The amendments replace the incurred loss impairment methodology in current US GAAP with a methodology (the current expected credit losses, or “CECL”, methodology) that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The CECL methodology utilizes a lifetime “expected credit loss” measurement objective for the recognition of credit losses for loans, held-to-maturity debt securities and other receivables measured at amortized cost at the time the financial asset is originated or acquired. The allowance for credit losses is adjusted each period for changes in expected lifetime credit losses. This methodology replaces the multiple existing impairment methods in current guidance, which generally require that a loss be incurred before it is recognized. Within the life cycle of a loan or other financial asset, this new guidance will generally result in the earlier recognition of the provision for credit losses and the related allowance for credit losses than current practice. For available-for-sale debt securities that the Company intends to hold and where fair value is less than cost, credit-related impairment, if any, will be recognized through an allowance for credit losses and adjusted each period for changes in credit risk. The effective date for these amendments is for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. In preparation for implementation of ASU 2016-13, the Company formed a cross functional team that assessed its data and system needs and evaluated the potential impact of adopting the new guidance. The Company anticipated a significant change in the processes and procedures to calculate the loan losses, including changes in assumptions and estimates to consider expected credit losses over the life of the loan versus the prior accounting practice that utilized the incurred loss model. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was signed in to law by the President of the United States and allows the option to temporarily defer or suspend the adoption of ASU 2016-13. During the deferral, a registrant would continue to use the incurred loss model for the allowance for loan and lease losses and would be in accordance with US GAAP. The Company has not elected to temporarily defer the adoption of ASU 2016-13 and adopted the new standard as of January 1, 2020. Upon adoption, the Company recorded an additional allowance for credit losses on loans of approximately $151.4 million and an adjustment to the reserve for unfunded commitments recorded in other liabilities of $24.0 million . The Company also recorded an additional allowance for credit losses on investment securities of $742,000 . The impact at adoption was reflected as an adjustment to beginning retained earnings, net of income taxes, in the amount of $128.1 million . The significant impact to the Company’s allowance for credit losses at the date of adoption was driven by the substantial amount of loans acquired held by the Company. The Company had approximately one third of total loans categorized as acquired at the adoption date with very little reserve allocated to them due to the previous incurred loss impairment methodology. As such, the amount of the CECL adoption impact was greater on the Company when compared to a non-acquisitive bank. In December 2018, the Federal Reserve, Office of the Comptroller of the Currency and Federal Deposit Insurance Corporation (“FDIC”) (collectively, the “agencies”) issued a final rule revising regulatory capital rules in anticipation of the adoption of ASU 2016-13 that provided an option to phase in over a three year period on a straight line basis the day-one impact on earnings and tier one capital (the “CECL Transition Provision”). In March 2020 and in response to the COVID-19 pandemic, the agencies issued a new regulatory capital rule revising the CECL Transition Provision to delay the estimated impact on regulatory capital stemming from the implementation of ASU 2016-13. The rule provides banking organizations that implement CECL before the end of 2020 the option to delay for two years an estimate of CECL’s effect on regulatory capital, followed by a three-year transition period (the “2020 CECL Transition Provision”). The Company elected to apply the 2020 CECL Transition Provision. In connection with the adoption of ASU 2016-13, the Company revised certain accounting policies and implemented certain accounting policy elections. The revised accounting policies are described below: Allowance for Credit Losses - Held-to-Maturity (“HTM”) Securities - The Company measures expected credit losses on HTM securities on a collective basis by major security type with each type sharing similar risk characteristics. The estimate of expected credit losses considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. The Company has made the election to exclude accrued interest receivable on HTM securities from the estimate of credit losses and report accrued interest separately on the consolidated balance sheets. See Note 3, Investment Securities, for additional information related to the Company’s allowance for credit losses on HTM securities. Allowance for Credit Losses - Available-for-Sale (“AFS”) Securities - For AFS securities in an unrealized loss position, the Company first evaluates whether it intends to sell, or whether it is more likely than not that it will be required to sell, the security before recovery of its amortized cost basis. If either of these criteria regarding intent or requirement to sell is met, the AFS security amortized cost basis is written down to fair value through income. If the criteria is not met, the Company is required to assess whether the decline in fair value has resulted from credit losses or noncredit-related factors. If the assessment indicates a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists, and an allowance for credit loss is recorded through income as a component of provision for credit loss expense. If the assessment indicates that a credit loss does not exist, the Company records the decline in fair value through other comprehensive income, net of related income tax effects. The Company has made the election to exclude accrued interest receivable on AFS securities from the estimate of credit losses and report accrued interest separately on the consolidated balance sheets. Changes in the allowance for credit losses are recorded as provision for (or reversal of) credit loss expense. Losses are charged against the allowance when management believes the uncollectibility of an AFS security is confirmed or when either of the criteria regarding intent or requirement to sell is met. See Note 3, Investment Securities, for additional information related to the Company’s allowance for credit losses on AFS securities. Loans - Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at their amortized cost basis, which is the unpaid principal balance outstanding, net of unearned income, deferred loan fees and costs, premiums and discounts associated with acquisition date fair value adjustments on acquired loans, and any direct principal charge-offs. The Company has made a policy election to exclude accrued interest from the amortized cost basis of loans and report accrued interest separately from the related loan balance on the consolidated balance sheets. Further information regarding accounting policies related to past due loans, non-accrual loans, and troubled-debt restructurings is presented in Note 5, Loans and Allowance for Credit Losses. The Company used the prospective transition approach for financial assets purchased with credit deterioration (“PCD”) that were previously classified as purchased credit impaired (“PCI”) and accounted for under Accounting Standards Codification (“ASC”) 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality . The Company increased the allowance for credit losses by approximately $5.4 million at adoption for the assets previously identified as PCI. In accordance with ASU 2016-13, the Company did not reassess whether PCI assets met the criteria of PCD assets as of the date of adoption. Collateral Dependent Loans - Loans that do not share risk characteristics are evaluated on an individual basis. For collateral dependent financial assets where the Company has determined that foreclosure of the collateral is probable, or where the borrower is experiencing financial difficulty and the Company expects repayment of the financial asset to be provided substantially through the operation or sale of the collateral, the allowance for credit loss is measured based on the difference between the fair value of the collateral and the amortized cost basis of the asset as of the measurement date. When repayment is expected to be from the operation of the collateral, expected credit losses are calculated as the amount by which the amortized cost basis of the financial asset exceeds the present value of expected cash flows from the operation of the collateral. When repayment is expected to be from the sale of the collateral, expected credit losses are calculated as the amount by which the amortized costs basis of the financial asset exceeds the fair value of the underlying collateral less estimated cost to sell. The allowance for credit losses may be zero if the fair value of the collateral at the measurement date exceeds the amortized cost basis of the financial asset. Allowance For Credit Losses - Off-Balance-Sheet Credit Exposures - The allowance for credit losses on off-balance-sheet credit exposures is a liability account representing expected credit losses over the contractual period for which the Company is exposed to credit risk resulting from a contractual obligation to extend credit. No allowance for credit loss is recognized if the Company has the unconditional right to cancel the obligation. The allowance for credit loss is reported as a component of accrued interest and other liabilities in the consolidated balance sheets. Adjustments to the allowance are reported in the income statement as a component of other operating expenses. Recently Issued Accounting Standards Reference Rate Reform – In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides relief for companies preparing for discontinuation of interest rates such as the London Interbank Offered Rate (“LIBOR”). LIBOR is a benchmark interest rate referenced in a variety of agreements that are used by numerous entities. After 2021, banks will no longer be required to report information that is used to determine LIBOR. As a result, LIBOR could be discontinued. Other interest rates used globally could also be discontinued for similar reasons. ASU 2020-04 provides optional expedients and exceptions to contracts, hedging relationships and other transactions affected by reference rate reform. The main provisions for contract modifications include optional relief by allowing the modification as a continuation of the existing contract without additional analysis and other optional expedients regarding embedded features. Optional expedients for hedge accounting permits changes to critical terms of hedging relationships and to the designated benchmark interest rate in a fair value hedge and also provides relief for assessing hedge effectiveness for cash flow hedges. Companies are able to apply ASU 2020-04 immediately; however, the guidance will only be available for a limited time (generally through December 31, 2022). As of March 31, 2020 , the Company has not made any modifications to hedges or other instruments that reference an interest rate that is expected to be discontinued. Income Taxes – In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), that removes certain exceptions for investments, intraperiod allocations and interim calculations, and adds guidance to reduce complexity in accounting for income taxes. ASU 2019-12 introduces the following new guidance: i) guidance to evaluate whether a step-up in tax basis of goodwill relates to a business combination in which book goodwill was recognized or a separate transaction and ii) a policy election to not allocate consolidated income taxes when a member of a consolidated tax return is not subject to income tax. Additionally, ASU 2019-12 changes the following current guidance: i) making an intraperiod allocation, if there is a loss in continuing operations and gains outside of continuing operations, ii) determining when a deferred tax liability is recognized after an investor in a foreign entity transitions to or from the equity method of accounting, iii) accounting for tax law changes and year-to-date losses in interim periods, and iv) determining how to apply the income tax guidance to franchise taxes that are partially based on income. ASU 2019-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating all of the amendments in ASU 2019-12 and has not yet determined the impact of this new standard. There have been no other significant changes to the Company’s accounting policies from the 2019 Form 10-K. Presently, the Company is not aware of any other changes to the Accounting Standards Codification that will have a material impact on its present or future financial position or results of operations.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Acquisitions	ACQUISITIONS The Landrum Company On October 31, 2019, the Company completed its merger with The Landrum Company (“Landrum”), pursuant to the terms of the Agreement and Plan of Merger dated as of July 30, 2019 (“Landrum Agreement”), at which time Landrum was merged with and into the Company, with the Company continuing as the surviving corporation. Pursuant to the terms of the Landrum Agreement, the shares of Landrum Class A Common Voting Stock, par value $0.01 per share, and Landrum Class B Common Nonvoting Stock, par value $0.01 per share, were converted into the right to receive, in the aggregate, approximately 17,350,000 shares of the Company’s common stock and each share of Landrum’s series E preferred stock was converted into the right to receive one share of the Company’s comparable series D preferred stock. The Company issued 17,349,722 shares of its common stock and 767 shares of its series D preferred stock, par value $0.01 per share, in exchange for all outstanding shares of Landrum capital stock to effect the merger. Prior to the acquisition, Landrum, headquartered in Columbia, Missouri, conducted banking business through its subsidiary bank, Landmark Bank, from 39 branches located in Missouri, Oklahoma and Texas. Including the effects of the acquisition method accounting adjustments, the Company acquired approximately $3.4 billion in assets, including approximately $2.0 billion in loans (inclusive of loan discounts), and approximately $3.0 billion in deposits. The systems conversion occurred on February 14, 2020, at which time Landmark Bank merged into Simmons Bank, with Simmons Bank as the surviving institution. Goodwill of $140.8 million was recorded as a result of the transaction. The merger strengthened the Company’s market share and brought forth additional opportunities in the Company’s current footprint, which gave rise to the goodwill recorded. The goodwill will not be deductible for tax purposes. A summary, at fair value, of the assets acquired and liabilities assumed in the Landrum transaction, as of the acquisition date, is as follows: (In thousands) Acquired from Landrum Fair Value Adjustments Fair Value Assets Acquired Cash and due from banks $ 215,285 $ — $ 215,285 Due from banks - time 248 — 248 Investment securities 1,021,755 4,228 1,025,983 Loans acquired 2,049,137 (43,651 ) 2,005,486 Allowance for loan losses (22,736 ) 22,736 — Foreclosed assets 373 (183 ) 190 Premises and equipment 63,878 18,867 82,745 Bank owned life insurance 19,206 — 19,206 Goodwill 407 (407 ) — Core deposit intangible — 24,345 24,345 Other intangibles 412 4,704 5,116 Other assets 33,924 (13,401 ) 20,523 Total assets acquired $ 3,381,889 $ 17,238 $ 3,399,127 Liabilities Assumed Deposits: Non-interest bearing transaction accounts $ 716,675 $ — $ 716,675 Interest bearing transaction accounts and savings deposits 1,465,429 — 1,465,429 Time deposits 867,197 299 867,496 Total deposits 3,049,301 299 3,049,600 Other borrowings 10,055 — 10,055 Subordinated debentures 34,794 (877 ) 33,917 Accrued interest and other liabilities 31,057 (484 ) 30,573 Total liabilities assumed 3,125,207 (1,062 ) 3,124,145 Equity 256,682 (256,682 ) — Total equity assumed 256,682 (256,682 ) — Total liabilities and equity assumed $ 3,381,889 $ (257,744 ) $ 3,124,145 Net assets acquired 274,982 Purchase price 415,779 Goodwill $ 140,797 The purchase price allocation and certain fair value measurements remain preliminary due to the timing of the merger. Management will continue to review the estimated fair values and evaluate the assumed tax positions. The Company expects to finalize its analysis of the acquired assets and assumed liabilities in this transaction over the next few months, within one year of the merger. Therefore, adjustments to the estimated amounts and carrying values may occur. The Company’s operating results include the operating results of the acquired assets and assumed liabilities of Landrum subsequent to the acquisition date. Reliance Bancshares, Inc. On April 12, 2019, the Company completed its merger with Reliance Bancshares, Inc. (“Reliance”), headquartered in the St. Louis, Missouri, metropolitan area, pursuant to the terms of the Agreement and Plan of Merger (“Reliance Agreement”), dated November 13, 2018, as amended February 11, 2019. In the merger, each outstanding share of Reliance common stock, as well as each Reliance common stock equivalent was canceled and converted into the right to receive shares of the Company’s common stock and/or cash in accordance with the terms of the Reliance Agreement. In addition, each share of Reliance’s Series A Preferred Stock and Series B Preferred Stock was converted into the right to receive one share of Simmons’ comparable Series A Preferred Stock or Series B Preferred Stock, respectively, and each share of Reliance’s Series C Preferred Stock was converted into the right to receive one share of Simmons’ comparable Series C Preferred Stock (unless the holder of such Series C Preferred Stock elected to receive alternate consideration in accordance with the Reliance Agreement). The Company issued 3,999,623 shares of its common stock and paid $62.7 million in cash to effect the merger. The Company also issued $42.0 million of its Series A Preferred Stock and Series B Preferred Stock. On May 13, 2019, the Company redeemed all of the preferred stock issued in connection with the merger, and paid all accrued and unpaid dividends up to the date of redemption. On October 29, 2019, the Company amended its Amended and Restated Articles of Incorporation to cancel the Series C Preferred Stock, having 140 authorized shares, of which no shares were ever issued or outstanding. Prior to the acquisition, Reliance conducted banking business through its subsidiary bank, Reliance Bank, from 22 branches located in Missouri and Illinois. Including the effects of the acquisition method accounting adjustments, the Company acquired approximately $1.5 billion in assets, including approximately $1.1 billion in loans (inclusive of loan discounts), and approximately $1.2 billion in deposits. Contemporaneously with the completion of the Reliance merger, Reliance Bank was merged into Simmons Bank, with Simmons Bank as the surviving institution. Goodwill of $78.5 million was recorded as a result of the transaction. The merger strengthened the Company’s market share and brought forth additional opportunities in the Company’s St. Louis metropolitan area footprint, which gave rise to the goodwill recorded. The goodwill will not be deductible for tax purposes. A summary, at fair value, of the assets acquired and liabilities assumed in the Reliance transaction, as of the acquisition date, is as follows: (In thousands) Acquired from Reliance Fair Value Adjustments Fair Value Assets Acquired Cash and due from banks $ 25,693 $ — $ 25,693 Due from banks - time 502 — 502 Investment securities 287,983 (1,873 ) 286,110 Loans acquired 1,138,527 (41,657 ) 1,096,870 Allowance for loan losses (10,808 ) 10,808 — Foreclosed assets 11,092 (5,180 ) 5,912 Premises and equipment 32,452 (3,001 ) 29,451 Bank owned life insurance 39,348 — 39,348 Core deposit intangible — 18,350 18,350 Other assets 25,165 6,911 32,076 Total assets acquired $ 1,549,954 $ (15,642 ) $ 1,534,312 (In thousands) Acquired from Reliance Fair Value Adjustments Fair Value Liabilities Assumed Deposits: Non-interest bearing transaction accounts $ 108,845 $ (33 ) $ 108,812 Interest bearing transaction accounts and savings deposits 639,798 — 639,798 Time deposits 478,415 (1,758 ) 476,657 Total deposits 1,227,058 (1,791 ) 1,225,267 Securities sold under agreement to repurchase 14,146 — 14,146 Other borrowings 162,900 (5,500 ) 157,400 Accrued interest and other liabilities 8,185 268 8,453 Total liabilities assumed 1,412,289 (7,023 ) 1,405,266 Equity 137,665 (137,665 ) — Total equity assumed 137,665 (137,665 ) — Total liabilities and equity assumed $ 1,549,954 $ (144,688 ) $ 1,405,266 Net assets acquired 129,046 Purchase price 207,539 Goodwill $ 78,493 During 2020, the Company finalized its analysis of the loans acquired along with other acquired assets and assumed liabilities. The Company’s operating results include the operating results of the acquired assets and assumed liabilities of Reliance subsequent to the acquisition date. The following is a description of the methods used to determine the fair values of significant assets and liabilities presented in the acquisitions above. Cash and due from banks and time deposits due from banks – The carrying amount of these assets is a reasonable estimate of fair value based on the short-term nature of these assets. Investment securities – Investment securities were acquired with an adjustment to fair value based upon quoted market prices if material. Otherwise, the carrying amount of these assets was deemed to be a reasonable estimate of fair value. Loans acquired – Fair values for loans were based on a discounted cash flow methodology that considered factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and current discount rates. The discount rates used for loans are based on current market rates for new originations of comparable loans and include adjustments for liquidity concerns. The discount rate does not include a factor for credit losses as that has been included in the estimated cash flows. Loans were grouped together according to similar characteristics and were treated in the aggregate when applying various valuation techniques. Foreclosed assets – These assets are presented at the estimated present values that management expects to receive when the properties are sold, net of related costs of disposal. Premises and equipment – Bank premises and equipment were acquired with an adjustment to fair value, which represents the difference between the Company’s current analysis of property and equipment values completed in connection with the acquisition and book value acquired. Bank owned life insurance – Bank owned life insurance is carried at its current cash surrender value, which is the most reasonable estimate of fair value. Goodwill – The consideration paid as a result of the acquisition exceeded the fair value of the assets acquired, resulting in an intangible asset, goodwill. Goodwill established prior to the acquisitions, if applicable, was written off. Core deposit intangible – This intangible asset represents the value of the relationships that the acquired banks had with their deposit customers. The fair value of this intangible asset was estimated based on a discounted cash flow methodology that gave appropriate consideration to expected customer attrition rates, cost of the deposit base and the net maintenance cost attributable to customer deposits. Any core deposit intangible established prior to the acquisitions, if applicable, was written off. Other intangibles – These intangible assets represent the value of the relationship that Landrum had with their trust and wealth management customers. The fair value of these intangible assets was estimated based on a combination of discounted cash flow methodology and a market valuation approach. Intangible assets for Landrum also included mortgage servicing rights. Other intangibles established prior to the acquisitions, if applicable, were written off. Other assets – The fair value adjustment results from certain assets whose value was estimated to be more or less than book value, such as certain prepaid assets, receivables and other miscellaneous assets. Otherwise, the carrying amount of these assets was deemed to be a reasonable estimate of fair value. Deposits – The fair values used for the demand and savings deposits that comprise the transaction accounts acquired, by definition equal the amount payable on demand at the acquisition date. The Company performed a fair value analysis of the estimated weighted average interest rate of the certificates of deposits compared to the current market rates and recorded a fair value adjustment for the difference when material. Securities sold under agreement to repurchase – The carrying amount of securities sold under agreement to repurchase is a reasonable estimate of fair value based on the short-term nature of these liabilities. Other borrowings – The fair value of other borrowings is estimated based on borrowing rates currently available to the Company for borrowings with similar terms and maturities. Subordinated debentures – The fair value of subordinated debentures is estimated based on borrowing rates currently available to the Company for borrowings with similar terms and maturities. Accrued interest and other liabilities – The adjustment establishes a liability for unfunded commitments equal to the fair value of that liability at the date of acquisition. The carrying amount of accrued interest and the remainder of other liabilities was deemed to be a reasonable estimate of fair value.

Investment Securities

Investment Securities	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investment Securities	INVESTMENT SECURITIES Held-to-maturity securities, which include any security for which the Company has the positive intent and ability to hold until maturity, are carried at historical cost adjusted for amortization of premiums and accretion of discounts. Premiums and discounts are amortized and accreted, respectively, to interest income using the constant yield method over the period to maturity. Available-for-sale securities, which include any security for which the Company has no immediate plan to sell but which may be sold in the future, are carried at fair value. Realized gains and losses, based on specifically identified amortized cost of the individual security, are included in other income. Unrealized gains and losses are recorded, net of related income tax effects, in stockholders’ equity, further discussed below. Premiums and discounts are amortized and accreted, respectively, to interest income using the constant yield method over the period to maturity. The amortized cost, fair value and allowance for credit losses of investment securities that are classified as HTM are as follows: (In thousands) Amortized Cost Allowance for Credit Losses Net Carrying Amount Gross Unrealized Gains Gross Unrealized (Losses) Estimated Fair Value Held-to-Maturity March 31, 2020 Mortgage-backed securities $ 27,121 $ — $ 27,121 $ 668 $ (1 ) $ 27,788 State and political subdivisions 26,082 (97 ) 25,985 981 (12 ) 26,954 Other securities 1,174 (312 ) 862 110 — 972 Total HTM $ 54,377 $ (409 ) $ 53,968 $ 1,759 $ (13 ) $ 55,714 (In thousands) Amortized Cost Allowance for Credit Losses Net Carrying Amount Gross Unrealized Gains Gross Unrealized (Losses) Estimated Fair Value December 31, 2019 Mortgage-backed securities $ 10,796 $ — $ 10,796 $ 71 $ (59 ) $ 10,808 State and political subdivisions 27,082 — 27,082 849 — 27,931 Other securities 3,049 — 3,049 67 — 3,116 Total HTM $ 40,927 $ — $ 40,927 $ 987 $ (59 ) $ 41,855 The amortized cost, fair value and allowance for credit losses of investment securities that are classified as AFS are as follows: (In thousands) Amortized Allowance for Credit Losses Gross Unrealized Gross Unrealized Estimated Fair Available-for-sale March 31, 2020 U.S. Treasury $ 425,032 $ — $ — $ (43 ) $ 424,989 U.S. Government agencies 161,473 — 707 (891 ) 161,289 Mortgage-backed securities 1,150,878 — 32,068 (3,109 ) 1,179,837 State and political subdivisions 659,350 (95 ) 20,243 (1,255 ) 678,243 Other securities 21,765 (174 ) 866 (175 ) 22,282 Total AFS $ 2,418,498 $ (269 ) $ 53,884 $ (5,473 ) $ 2,466,640 December 31, 2019 U.S. Treasury $ 449,729 $ — $ 112 $ (112 ) $ 449,729 U.S. Government agencies 194,207 — 1,313 (1,271 ) 194,249 Mortgage-backed securities 1,738,584 — 8,510 (4,149 ) 1,742,945 State and political subdivisions 860,539 — 20,983 (998 ) 880,524 Other securities 20,092 — 822 (18 ) 20,896 Total AFS $ 3,263,151 $ — $ 31,740 $ (6,548 ) $ 3,288,343 Accrued interest receivable on HTM and AFS securities at March 31, 2020 was $334,000 and $9.7 million , respectively, and is included in interest receivable on the consolidated balance sheets. The Company has made the election to exclude all accrued interest receivable from securities from the estimate of credit losses. The following table summarizes the Company’s AFS investments in an unrealized loss position for which an allowance for credit loss has not been recorded as of March 31, 2020 , aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total (In thousands) Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Available-for-sale U.S. Treasury $ 424,989 $ (43 ) $ — $ — $ 424,989 $ (43 ) U.S. Government agencies — — 58,056 (891 ) 58,056 (891 ) Mortgage-backed securities 57,718 (1,318 ) 74,523 (1,791 ) 132,241 (3,109 ) State and political subdivisions 24,813 (1,157 ) 425 (4 ) 25,238 (1,161 ) Total AFS $ 507,520 $ (2,518 ) $ 133,004 $ (2,686 ) $ 640,524 $ (5,204 ) As of March 31, 2020 , the Company’s investment portfolio included $2.5 billion of AFS securities, of which $640.5 million , or 26.0% were in an unrealized loss position that are not deemed to have credit losses. The majority of these unrealized losses were related to the Company’s mortgage-backed securities, which are issued and guaranteed by U.S. government-sponsored entities and agencies, and the Company’s state and political securities, specifically investments in insured fixed rate municipal bonds meaning issuers continue to make timely principal and interest payments under the contractual terms of the securities. Furthermore, the decline in fair value for each of the above AFS securities is attributable to the rates for those investments yielding less than current market rates. Management does not believe any of the securities are impaired due to reasons of credit quality. Management believes the declines in fair value for the securities are temporary. Management does not have the intent to sell the securities, and management believes it is more likely than not the Company will not have to sell the securities before recovery of their amortized cost basis. Allowance for Credit Losses All of the mortgage-backed securities held by the Company are issued by U.S. government-sponsored entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government, are highly rated by major rating agencies and have a long history of no credit losses. Accordingly, no allowance for credit losses has been recorded for these securities. Regarding securities issued by state and political subdivisions and other HTM securities, management considers (i) issuer bond ratings, (ii) historical loss rates for given bond ratings, (iii) whether issuers continue to make timely principal and interest payments under the contractual terms of the securities, (iv) internal forecasts, (v) whether or not such securities provide insurance or other credit enhancement or pre-refunded by the issuers. The following table details activity in the allowance for credit losses by investment security type for the three months ended March 31, 2020 on the Company’s HTM and AFS securities held. (In thousands) State and Political Subdivisions Other Securities Total Held-to-Maturity Balance, January 1, 2020 $ — $ — $ — Impact of ASU 2016-13 adoption 58 311 369 Provision for credit loss expense 39 1 40 Balance, March 31, 2020 $ 97 $ 312 $ 409 Available-for-sale Balance, January 1, 2020 $ — $ — $ — Impact of ASU 2016-13 adoption 373 — 373 Credit losses on securities not previously recorded 44 174 218 Net increase (decrease) in allowance on previously impaired securities (322 ) — (322 ) Balance, March 31, 2020 $ 95 $ 174 $ 269 During the three months ended March 31, 2020 , the provision for credit losses was reduced by $104,000 related to AFS securities. The following table summarizes bond ratings for the Company’s HTM portfolio issued by state and political subdivisions and other securities as of March 31, 2020 : State and Political Subdivisions (In thousands) Not Guaranteed or Pre-Refunded Other Credit Enhancement or Insurance Pre-Refunded Total Other Securities Aaa/AAA $ 2,111 $ — $ — $ 2,111 $ — Aa/AA 12,596 6,203 285 19,084 — A 766 929 — 1,695 — Not Rated 2,323 370 499 3,192 1,174 Total $ 17,796 $ 7,502 $ 784 $ 26,082 $ 1,174 Historical loss rates associated with securities having similar grades as those in the Company’s portfolio have generally not been significant. Pre-refunded securities have been defeased by the issuer and are fully secured by cash and/or U.S. Treasury securities held in escrow for payment to holders when the underlying call dates of the securities are reached. Securities with other credit enhancement or insurance continue to make timely principal and interest payments under the contractual terms of the securities. Accordingly, no allowance for credit losses has been recorded for these securities as there is no current expectation of credit losses related to these securities. Income earned on securities for the three months ended March 31, 2020 and 2019 , is as follows: Three Months Ended (In thousands) 2020 2019 Taxable: Held-to-maturity $ 171 $ 438 Available-for-sale 12,581 11,520 Non-taxable: Held-to-maturity 72 1,162 Available-for-sale 6,119 3,161 Total $ 18,943 $ 16,281 The amortized cost and estimated fair value by maturity of securities are shown in the following table. Securities are classified according to their contractual maturities without consideration of principal amortization, potential prepayments or call options. Accordingly, actual maturities may differ from contractual maturities. Held-to-Maturity Available-for-Sale (In thousands) Amortized Cost Fair Value Amortized Cost Fair Value One year or less $ 4,543 $ 4,563 $ 437,199 $ 437,187 After one through five years 15,414 15,769 34,541 34,889 After five through ten years 7,299 7,594 108,605 109,611 After ten years — — 686,714 703,839 Securities not due on a single maturity date 27,121 27,788 1,150,878 1,179,837 Other securities (no maturity) — — 561 1,277 Total $ 54,377 $ 55,714 $ 2,418,498 $ 2,466,640 The carrying value, which approximates the fair value, of securities pledged as collateral, to secure public deposits and for other purposes, amounted to $1.74 billion at March 31, 2020 and $1.73 billion at December 31, 2019 . There were approximately $32.1 million of gross realized gains and $2,080 of gross realized losses from the sale of securities during the three months ended March 31, 2020 . During the first quarter of 2020, the Company sold approximately $1.1 billion of investment securities to create additional liquidity. There were approximately $2.7 million of gross realized gains and no gross realized losses from the sale of securities during the three months ended March 31, 2019 . The income tax expense/benefit related to security gain/losses was 26.135% of the gross amounts in 2020 and 2019.

Other Assets and Other Liabilit

Other Assets and Other Liabilities Held for Sale	3 Months Ended
	Mar. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets and Other Liabilities Held for Sale	OTHER ASSETS AND OTHER LIABILITIES HELD FOR SALE Colorado Branch Sale On February 10, 2020, the Company’s subsidiary bank, Simmons Bank, entered into a Branch Purchase and Assumption Agreement (the “First Western Agreement”) with First Western Trust Bank (“First Western”), a wholly-owned subsidiary of First Western Financial, Inc., pursuant to which First Western will purchase certain assets and assume certain liabilities (the “Colorado Branch Sale”) associated with four Simmons Bank locations in Denver, Englewood, Highlands Ranch, and Lone Tree, Colorado (collectively, the “Colorado Branches”). Pursuant to the terms of the First Western Agreement, First Western has agreed to assume certain deposit liabilities and to acquire certain loans, as well as cash, personal property and other fixed assets associated with the Colorado Branches. The combined loan and deposit balances of the Colorado Branches (excluding certain loans and deposits not subject to the Colorado Branch Sale) as of March 31, 2020 , were approximately $114.9 million and $58.4 million , respectively. Pursuant to the terms and subject to the conditions of the First Western Agreement, the purchase price for the transaction will be computed as the difference of (A) the sum of (i) the aggregate balance of the deposits to be assumed, together with accrued and unpaid interest thereon, (ii) the amount of certain accrued expenses, and (iii) the amount of certain other liabilities to be assumed, together with accrued and unpaid interest thereon, and (B) the sum of (i) the aggregate outstanding principal balance of the loans to be acquired, together with accrued and unpaid interest thereon, (ii) the aggregate amount of cash on hand, (iii) the amount of certain prepaid expenses, and (iv) the aggregate net book value of the personal property and ATMs to be acquired. The purchase price is subject to a customary post-closing adjustment based on the delivery within 30 calendar days following the closing date of a final closing statement setting forth the purchase price and any necessary adjustment payment amount. Additionally, First Western will pay a premium to Simmons Bank in an amount equal to the average aggregate daily closing balance of the deposits to be acquired for the 30-business day period prior to the closing date multiplied by the Applicable Percentage. The “Applicable Percentage” equals (1) if the Colorado Branch Sale is completed on or before May 31, 2020, 6.06% , (2) if the Colorado Branch Sale is completed after May 31, 2020, but on or before July 31, 2020, 7.06% , or (3) if the Colorado Branch Sale is completed after July 31, 2020, 8.06% . The completion of the Colorado Branch Sale is subject to certain customary closing conditions. Subject to the satisfaction of such conditions, First Western and Simmons Bank expect to close the Colorado Branch Sale in the second quarter of 2020. Texas Branch Sale On December 20, 2019, the Company’s subsidiary bank, Simmons Bank, entered into a Branch Purchase and Assumption Agreement (the “Spirit Agreement”) with Spirit of Texas Bank, SSB (“Spirit”), a wholly-owned subsidiary of Spirit of Texas Bancshares, Inc. On February 28, 2020, Spirit completed its purchase of certain assets and assumption of certain liabilities (“Texas Branch Sale”) associated with five Simmons Bank locations in Austin, San Antonio, and Tilden, Texas (collectively, the “Texas Branches”). Pursuant to the terms of the Spirit Agreement, Spirit assumed certain deposit liabilities and acquired certain loans, as well as cash, real property, personal property and other fixed assets associated with the Texas Branches. The Company recognized a gain of $5.9 million on the sale.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
Loans and Allowance for Loan Losses	LOANS AND ALLOWANCE FOR CREDIT LOSSES At March 31, 2020 , the Company’s loan portfolio was $14.37 billion , compared to $14.43 billion at December 31, 2019 . The various categories of loans are summarized as follows: (In thousands) March 31, 2020 December 31, 2019 Consumer: Credit cards $ 188,596 $ 204,802 Other consumer 267,870 249,195 Total consumer 456,466 453,997 Real Estate: Construction and development 2,024,118 2,248,673 Single family residential 2,343,543 2,414,753 Other commercial 6,466,104 6,358,514 Total real estate 10,833,765 11,021,940 Commercial: Commercial 2,314,472 2,451,119 Agricultural 191,535 191,525 Total commercial 2,506,007 2,642,644 Other 578,039 307,123 Total loans $ 14,374,277 $ 14,425,704 The above table presents total loans at amortized cost. The difference between amortized cost and unpaid principal balance is primarily premiums and discounts associated with acquisition date fair value adjustments on acquired loans as well as net deferred origination fees totaling $72.4 million and $91.6 million at March 31, 2020 and December 31, 2019 , respectively. Accrued interest on loans, which is excluded from the amortized cost of loans held for investment, totaled $47.0 million and $48.9 million at March 31, 2020 and December 31, 2019 , respectively, and is included in interest receivable on the consolidated balance sheets. Loan Origination/Risk Management – The Company seeks to manage its credit risk by diversifying its loan portfolio, determining that borrowers have adequate sources of cash flow for loan repayment without liquidation of collateral; obtaining and monitoring collateral; providing an adequate allowance for credit losses by regularly reviewing loans through the internal loan review process. The loan portfolio is diversified by borrower, purpose and industry. The Company seeks to use diversification within the loan portfolio to reduce its credit risk, thereby minimizing the adverse impact on the portfolio if weaknesses develop in either the economy or a particular segment of borrowers. Collateral requirements are based on credit assessments of borrowers and may be used to recover the debt in case of default. Consumer – The consumer loan portfolio consists of credit card loans and other consumer loans. Credit card loans are diversified by geographic region to reduce credit risk and minimize any adverse impact on the portfolio. Although they are regularly reviewed to facilitate the identification and monitoring of creditworthiness, credit card loans are unsecured loans, making them more susceptible to be impacted by economic downturns resulting in increasing unemployment. Other consumer loans include direct and indirect installment loans and overdrafts. Loans in this portfolio segment are sensitive to unemployment and other key consumer economic measures. Real estate – The real estate loan portfolio consists of construction and development loans, single family residential loans and commercial loans. Construction and development loans (“C&D”) and commercial real estate loans (“CRE”) can be particularly sensitive to valuation of real estate. Commercial real estate cycles are inevitable. The long planning and production process for new properties and rapid shifts in business conditions and employment create an inherent tension between supply and demand for commercial properties. While general economic trends often move individual markets in the same direction over time, the timing and magnitude of changes are determined by other forces unique to each market. CRE cycles tend to be local in nature and longer than other credit cycles. Factors influencing the CRE market are traditionally different from those affecting residential real estate markets; thereby making predictions for one market based on the other difficult. Additionally, submarkets within commercial real estate – such as office, industrial, apartment, retail and hotel – also experience different cycles, providing an opportunity to lower the overall risk through diversification across types of CRE loans. Management realizes that local demand and supply conditions will also mean that different geographic areas will experience cycles of different amplitude and length. The Company monitors these loans closely. Commercial – The commercial loan portfolio includes commercial and agricultural loans, representing loans to commercial customers and farmers for use in normal business or farming operations to finance working capital needs, equipment purchases or other expansion projects. Collection risk in this portfolio is driven by the creditworthiness of the underlying borrowers, particularly cash flow from customers’ business or farming operations. The Company continues its efforts to keep loan terms short, reducing the negative impact of upward movement in interest rates. Term loans are generally set up with one or three year balloons, and the Company has instituted a pricing mechanism for commercial loans. It is standard practice to require personal guaranties on commercial loans for closely-held or limited liability entities. Nonaccrual and Past Due Loans – Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. Loans are placed on nonaccrual status when, in management’s opinion, the borrower may be unable to meet payment obligations as they become due, as well as when required by regulatory provisions. Loans may be placed on nonaccrual status regardless of whether or not such loans are considered past due. When interest accrual is discontinued, all unpaid accrued interest is reversed. Interest income is subsequently recognized only to the extent cash payments are received in excess of principal due. Loans are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured. The amortized cost basis of nonaccrual loans segregated by class of loans are as follows: (In thousands) March 31, 2020 December 31, 2019 Consumer: Credit cards $ 265 $ 382 Other consumer 2,111 1,705 Total consumer 2,376 2,087 Real estate: Construction and development 6,604 5,289 Single family residential 30,829 27,695 Other commercial 36,428 16,582 Total real estate 73,861 49,566 Commercial: Commercial 78,944 40,924 Agricultural 682 753 Total commercial 79,626 41,677 Total $ 155,863 $ 93,330 Nonaccrual loans for which there is no related allowance for credit losses as of March 31, 2020 had an amortized cost of $22.4 million . These loans are individually assessed and do not hold an allowance due to being adequately collateralized under the collateral-dependent valuation method. An age analysis of the amortized cost basis of past due loans, including nonaccrual loans, segregated by class of loans is as follows: (In thousands) Gross 30-89 Days Past Due 90 Days or More Past Due Total Past Due Current Total Loans 90 Days Past Due & Accruing March 31, 2020 Consumer: Credit cards $ 866 $ 325 $ 1,191 $ 187,405 $ 188,596 $ 115 Other consumer 4,540 1,131 5,671 262,199 267,870 — Total consumer 5,406 1,456 6,862 449,604 456,466 115 Real estate: Construction and development 2,713 5,013 7,726 2,016,392 2,024,118 — Single family residential 31,236 15,246 46,482 2,297,061 2,343,543 321 Other commercial 23,524 10,673 34,197 6,431,907 6,466,104 1 Total real estate 57,473 30,932 88,405 10,745,360 10,833,765 322 Commercial: Commercial 16,361 25,130 41,491 2,272,981 2,314,472 723 Agricultural 377 560 937 190,598 191,535 — Total commercial 16,738 25,690 42,428 2,463,579 2,506,007 723 Other — — — 578,039 578,039 — Total $ 79,617 $ 58,078 $ 137,695 $ 14,236,582 $ 14,374,277 $ 1,160 December 31, 2019 Consumer: Credit cards $ 848 $ 641 $ 1,489 $ 203,313 $ 204,802 $ 259 Other consumer 4,884 735 5,619 243,576 249,195 — Total consumer 5,732 1,376 7,108 446,889 453,997 259 Real estate: Construction and development 5,792 1,078 6,870 2,241,803 2,248,673 — Single family residential 26,318 13,789 40,107 2,374,646 2,414,753 597 Other commercial 7,645 6,450 14,095 6,344,419 6,358,514 — Total real estate 39,755 21,317 61,072 10,960,868 11,021,940 597 Commercial: Commercial 10,579 13,551 24,130 2,426,989 2,451,119 — Agricultural 1,223 456 1,679 189,846 191,525 — Total commercial 11,802 14,007 25,809 2,616,835 2,642,644 — Other — — — 307,123 307,123 — Total $ 57,289 $ 36,700 $ 93,989 $ 14,331,715 $ 14,425,704 $ 856 The following table presents information pertaining to impaired loans as of December 31, 2019 , in accordance with previous US GAAP prior to the adoption of ASU 2016-13. (In thousands) Unpaid Contractual Principal Balance Recorded Investment With No Allowance Recorded Investment With Allowance Total Recorded Investment Related Allowance Average Investment in Impaired Loans Interest Income Recognized December 31, 2019 Three Months Ended Consumer: Credit cards $ 382 $ 382 $ — $ 382 $ — $ 317 $ 30 Other consumer 1,537 1,378 — 1,378 — 1,857 13 Total consumer 1,919 1,760 — 1,760 — 2,174 43 Real estate: Construction and development 4,648 4,466 72 4,538 4 1,920 14 Single family residential 19,466 15,139 2,963 18,102 42 13,703 98 Other commercial 10,645 4,713 3,740 8,453 694 8,992 64 Total real estate 34,759 24,318 6,775 31,093 740 24,615 176 Commercial: Commercial 53,436 6,582 28,998 35,580 5,007 20,739 148 Agricultural 525 383 116 499 — 1,147 8 Total commercial 53,961 6,965 29,114 36,079 5,007 21,886 156 Total $ 90,639 $ 33,043 $ 35,889 $ 68,932 $ 5,747 $ 48,675 $ 375 When the Company restructures a loan to a borrower that is experiencing financial difficulty and grants a concession that it would not otherwise consider, a “troubled debt restructuring” (“TDR”) results and the Company classifies the loan as a TDR. The Company grants various types of concessions, primarily interest rate reduction and/or payment modifications or extensions, with an occasional forgiveness of principal. Once an obligation has been restructured because of such credit problems, it continues to be considered a TDR until paid in full; or, if an obligation yields a market interest rate and no longer has any concession regarding payment amount or amortization, then it is not considered a TDR at the beginning of the calendar year after the year in which the improvement takes place. The Company returns TDRs to accrual status only if (1) all contractual amounts due can reasonably be expected to be repaid within a prudent period, and (2) repayment has been in accordance with the contract for a sustained period, typically at least six months. The provisions in the CARES Act included an election to not apply the guidance on accounting for TDRs to loan modifications, such as extensions or deferrals, related to COVID-19 made between March 1, 2020 and the earlier of (i) December 31, 2020 or (ii) 60 days after the President terminates the COVID-19 national emergency declaration. The relief can only be applied to modifications for borrowers that were not more than 30 days past due as of December 31, 2019. The Company elected to adopt these provisions of the CARES Act. See discussion of the loans modified under the CARES Act in Note 24, Recent Events. TDRs are individually evaluated for expected credit losses. The Company assesses the exposure for each modification, either by the fair value of the underlying collateral or the present value of expected cash flows, and determines if a specific allowance for credit losses is needed. The following table presents a summary of TDRs segregated by class of loans. Accruing TDR Loans Nonaccrual TDR Loans Total TDR Loans (Dollars in thousands) Number Balance Number Balance Number Balance March 31, 2020 Real estate: Construction and development — $ — 1 $ 71 1 $ 71 Single-family residential 7 898 12 904 19 1,802 Other commercial 1 455 2 75 3 530 Total real estate 8 1,353 15 1,050 23 2,403 Commercial: Commercial 4 2,757 3 73 7 2,830 Total commercial 4 2,757 3 73 7 2,830 Total 12 $ 4,110 18 $ 1,123 30 $ 5,233 December 31, 2019 Real estate: Construction and development — $ — 1 $ 72 1 $ 72 Single-family residential 7 1,151 12 671 19 1,822 Other commercial 1 476 2 80 3 556 Total real estate 8 1,627 15 823 23 2,450 Commercial: Commercial 4 2,784 3 79 7 2,863 Total commercial 4 2,784 3 79 7 2,863 Total 12 $ 4,411 18 $ 902 30 $ 5,313 There were no loans restructured as TDRs during the three month periods ended March 31, 2020 or 2019 . There were no loans considered TDRs for which a payment default occurred during the three months ended March 31, 2020 . There was one commercial loan considered a TDR for which a payment default occurred during the three months ended March 31, 2019 . A charge-off of approximately $138,000 was recorded for this loan. The Company defines a payment default as a payment received more than 90 days after its due date. There were no TDRs with pre-modification loan balances for which OREO was received in full or partial satisfaction of the loans during the three month periods ended March 31, 2020 or 2019 . At March 31, 2020 and December 31, 2019 , the Company had $5,301,000 and $5,789,000 , respectively, of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process. At March 31, 2020 and December 31, 2019 , the Company had $2,672,000 and $4,458,000 , respectively, of OREO secured by residential real estate properties. Credit Quality Indicators – As part of the on-going monitoring of the credit quality of the Company’s loan portfolio, management tracks certain credit quality indicators including trends related to (i) the weighted-average risk rating of commercial and real estate loans, (ii) the level of classified commercial and real estate loans, (iii) net charge-offs, (iv) non-performing loans (see details above) and (v) the general economic conditions of the Company’s local markets. The Company utilizes a risk rating matrix to assign a risk rate to each of its commercial and real estate loans. Loans are rated on a scale of 1 to 8. Risk ratings are updated on an ongoing basis and are subject to change by continuous loan monitoring processes including lending management monitoring, executive management and board committee oversight, and independent credit review. A description of the general characteristics of the 8 risk ratings is as follows: • Risk Rate 1 – Pass (Excellent) – This category includes loans which are virtually free of credit risk. Borrowers in this category represent the highest credit quality and greatest financial strength. • Risk Rate 2 – Pass (Good) - Loans under this category possess a nominal risk of default. This category includes borrowers with strong financial strength and superior financial ratios and trends. These loans are generally fully secured by cash or equivalents (other than those rated “excellent”). • Risk Rate 3 – Pass (Acceptable – Average) - Loans in this category are considered to possess a normal level of risk. Borrowers in this category have satisfactory financial strength and adequate cash flow coverage to service debt requirements. If secured, the perfected collateral should be of acceptable quality and within established borrowing parameters. • Risk Rate 4 – Pass (Monitor) - Loans in the Watch (Monitor) category exhibit an overall acceptable level of risk, but that risk may be increased by certain conditions, which represent “red flags”. These “red flags” require a higher level of supervision or monitoring than the normal “Pass” rated credit. The borrower may be experiencing these conditions for the first time, or it may be recovering from weakness, which at one time justified a higher rating. These conditions may include: weaknesses in financial trends; marginal cash flow; one-time negative operating results; non-compliance with policy or borrowing agreements; poor diversity in operations; lack of adequate monitoring information or lender supervision; questionable management ability/stability. • Risk Rate 5 – Special Mention - A loan in this category has potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the asset or in the institution’s credit position at some future date. Special Mention loans are not adversely classified (although they are “criticized”) and do not expose an institution to sufficient risk to warrant adverse classification. Borrowers may be experiencing adverse operating trends, or an ill-proportioned balance sheet. Non-financial characteristics of a Special Mention rating may include management problems, pending litigation, a non-existent, or ineffective loan agreement or other material structural weakness, and/or other significant deviation from prudent lending practices. • Risk Rate 6 – Substandard - A Substandard loan is inadequately protected by the current sound worth and paying capacity of the borrower or of the collateral pledged, if any. Loans so classified must have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt. The loans are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. This does not imply ultimate loss of the principal, but may involve burdensome administrative expenses and the accompanying cost to carry the loan. • Risk Rate 7 – Doubtful - A loan classified Doubtful has all the weaknesses inherent in a substandard loan except that the weaknesses make collection or liquidation in full (on the basis of currently existing facts, conditions, and values) highly questionable and improbable. Doubtful borrowers are usually in default, lack adequate liquidity, or capital, and lack the resources necessary to remain an operating entity. The possibility of loss is extremely high, but because of specific pending events that may strengthen the asset, its classification as loss is deferred. Pending factors include: proposed merger or acquisition; liquidation procedures; capital injection; perfection of liens on additional collateral; and refinancing plans. Loans classified as Doubtful are placed on nonaccrual status. • Risk Rate 8 – Loss - Loans classified Loss are considered uncollectible and of such little value that their continuance as bankable assets is not warranted. This classification does not mean that the loans has absolutely no recovery or salvage value, but rather it is not practical or desirable to defer writing off this basically worthless loan, even though partial recovery may be affected in the future. Borrowers in the Loss category are often in bankruptcy, have formally suspended debt repayments, or have otherwise ceased normal business operations. Loans should be classified as Loss and charged-off in the period in which they become uncollectible. The Company monitors credit quality in the consumer portfolio by delinquency status. The delinquency status of loans is updated daily. A description of the delinquency credit quality indicators is as follows: • Current - Loans in this category are either current in payments or are under 30 days past due. These loans are considered to have a normal level of risk. • 30-89 Days Past Due - Loans in this category are between 30 and 89 days past due and are subject to the Company’s loss mitigation process. These loans are considered to have a moderate level of risk. • 90+ Days Past Due - Loans in this category are over 90 days past due and are placed on nonaccrual status. These loans have been subject to the Company’s loss mitigation process and foreclosure and/or charge-off proceedings have commenced. The following table presents a summary of loans by credit quality indicator as of March 31, 2020 segregated by class of loans. Term Loans Amortized Cost Basis by Origination Year (In thousands) 2020 (YTD) 2019 2018 2017 2016 2015 and Prior Lines of Credit Amortized Cost Basis Lines of Credit Converted to Term Loans Amortized Cost Basis Total March 31, 2020 Consumer - credit cards Delinquency: 30-89 days past due $ — $ — $ — $ — $ — $ — $ 866 $ — $ 866 90+ days past due — — — — — — 325 — 325 Total consumer - credit cards — — — — — — 1,191 — 1,191 Consumer - other Delinquency: 30-89 days past due 47 1,109 636 1,188 1,182 251 128 — 4,541 90+ days past due — 147 97 446 203 60 178 — 1,131 Total consumer - other 47 1,256 733 1,634 1,385 311 306 — 5,672 Real estate - C&D Risk rating: 5 internal grade — 45 19 1,957 21 — — — 2,042 6 internal grade — 3,569 620 206 432 626 2,401 209 8,063 7 internal grade — — — — — — — — — Total real estate - C&D — 3,614 639 2,163 453 626 2,401 209 10,105 Real estate - SF residential Delinquency: 30-89 days past due 33 4,672 6,168 4,648 5,010 8,233 2,471 — 31,235 90+ days past due — 2,115 4,074 2,394 1,829 3,748 1,086 — 15,246 Total real estate - SF residential 33 6,787 10,242 7,042 6,839 11,981 3,557 — 46,481 Real estate - other commercial Risk rating: 5 internal grade 1,037 23,628 2,116 985 4,845 3,379 12,477 — 48,467 6 internal grade 2,728 16,060 17,211 4,369 6,860 20,059 37,552 1,037 105,876 7 internal grade — — — — — — — — — Total real estate - other commercial 3,765 39,688 19,327 5,354 11,705 23,438 50,029 1,037 154,343 Commercial Risk rating: 5 internal grade — 209 14 270 407 77 25,418 — 26,395 6 internal grade 16 11,925 6,994 16,480 1,264 764 54,993 743 93,179 7 internal grade — — — — — — — — — Total commercial 16 12,134 7,008 16,750 1,671 841 80,411 743 119,574 Commercial - agriculture Risk rating: 5 internal grade — 67 — 25 12 — 17 — 121 6 internal grade — 115 177 169 88 8 230 — 787 7 internal grade — — — — — — — — — Total commercial - agriculture — 182 177 194 100 8 247 — 908 Total $ 3,861 $ 63,661 $ 38,126 $ 33,137 $ 22,153 $ 37,205 $ 138,142 $ 1,989 $ 338,274 The following table presents a summary of loans by credit risk rating as of December 31, 2019 segregated by class of loans. (In thousands) Risk Rate 1-4 Risk Rate 5 Risk Rate 6 Risk Rate 7 Risk Rate 8 Total December 31, 2019 Consumer: Credit cards $ 204,161 $ — $ 641 $ — $ — $ 204,802 Other consumer 247,668 — 2,026 — — 249,694 Total consumer 451,829 — 2,667 — — 454,496 Real estate: Construction and development 2,229,019 70 7,735 — 37 2,236,861 Single family residential 2,394,284 6,049 41,601 130 — 2,442,064 Other commercial 6,068,425 69,745 67,429 — — 6,205,599 Total real estate 10,691,728 75,864 116,765 130 37 10,884,524 Commercial: Commercial 2,384,263 26,713 84,317 43 180 2,495,516 Agricultural 309,741 41 5,672 — — 315,454 Total commercial 2,694,004 26,754 89,989 43 180 2,810,970 Other 275,714 — — — — 275,714 Total $ 14,113,275 $ 102,618 $ 209,421 $ 173 $ 217 $ 14,425,704 Allowance for Credit Losses Allowance for Credit Losses – The allowance for credit losses is a reserve established through a provision for credit losses charged to expense, which represents management’s best estimate of lifetime expected losses based on reasonable and supportable forecasts, historical loss experience, and other qualitative considerations. The allowance, in the judgment of management, is necessary to reserve for expected loan losses and risks inherent in the loan portfolio. The Company’s allowance for credit loss methodology includes reserve factors calculated to estimate current expected credit losses to amortized cost balances over the remaining contractual life of the portfolio, adjusted for the effective interest rate used to discount prepayments, in accordance with ASC Topic 326-20, Financial Instruments - Credit Losses . Accordingly, the methodology is based on the Company’s reasonable and supportable economic forecasts, historical loss experience, and other qualitative adjustments. Loans with similar risk characteristics such as loan type, collateral type, and internal risk ratings are aggregated into homogeneous segments for assessment. Reserve factors are based on estimated probability of default and loss given default for each segment. The estimates are determined based on economic forecasts over the reasonable and supportable forecast period based on projected performance of economic variables that have a statistical correlation with the historical loss experience of the segments. For contractual periods that extend beyond the one-year forecast period, the estimates revert to average historical loss experiences over a one-year period on a straight-line basis. The Company also includes qualitative adjustments to the allowance based on factors and considerations that have not otherwise been fully accounted for. Qualitative adjustments include, but are not limited to: • Changes in asset quality - Adjustments related to trending credit quality metrics including delinquency, nonperforming loans, charge-offs, and risk ratings that may not be fully accounted for in the reserve factor. • Changes in the nature and volume of the portfolio - Adjustments related to current changes in the loan portfolio that are not fully represented or accounted for in the reserve factors. • Changes in lending and loan monitoring policies and procedures - Adjustments related to current changes in lending and loan monitoring procedures as well as review of specific internal policy compliance metrics. • Change in the experience, ability, and depth of lending management and other relevant staff - Adjustments to measure increasing or decreasing credit risk related to lending and loan monitoring management. • Changes in the value of underlying collateral of collateralized loans - Adjustments related to improving or deterioration of the value of underlying collateral that are not fully captured in the reserve factors. • Changes in and the existence and effect of any concentrations of credit - Adjustments related to credit risk of specific industries that are not fully captured in the reserve factors. • Changes in regional and local economic and business conditions and developments - Adjustments related to expected and current economic conditions at a regional or local-level that are not fully captured within the Company’s reasonable and supportable forecast. • Data imprecisions due to limited historical loss data - Adjustments related to limited historical loss data that is representative of the collective loan portfolio. Loans that do not share similar risk characteristics are evaluated on an individual basis. These evaluations are typically performed on loans with a deteriorated internal risk rating or are classified as a troubled debt restructuring. The allowance for credit loss is determined based on several methods including estimating the fair value of the underlying collateral or the present value of expected cash flows. For a collateral dependent loan, the Company’s evaluation process includes a valuation by appraisal or other collateral analysis adjusted for selling costs, when appropriate. This valuation is compared to the remaining outstanding principal balance of the loan. If a loss is determined to be probable, the loss is included in the allowance for credit losses as a specific allocation. If the loan is not collateral dependent, the measurement of loss is based on the difference between the expected and contractual future cash flows of the loan. Loans for which the repayment is expected to be provided substantially through the operation or sale of collateral and where the borrower is experiencing financial difficulty had an amortized cost of $75.7 million as further detailed in the table below. The collateral securing these loans consist of commercial real estate properties, residential properties, other business assets, and secured energy production assets. (In thousands) Real Estate Collateral Energy Other Collateral Total Construction and development $ 3,078 $ — $ — $ 3,078 Single family residential 3,586 — — 3,586 Other commercial real estate 16,984 — — 16,984 Commercial — 43,573 8,449 52,022 Total $ 23,648 $ 43,573 $ 8,449 $ 75,670 The following table details activity in the allowance for credit losses by portfolio segment for loans for the three months ended March 31, 2020 . Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. (In thousands) Commercial Real Estate Credit Card Other Consumer and Other Total Three Months Ended March 31, 2020 Allowance for credit losses: Beginning balance, prior to adoption of CECL $ 22,863 $ 39,161 $ 4,051 $ 2,169 $ 68,244 Impact of CECL adoption 22,733 114,314 2,232 12,098 151,377 Provision for credit loss expense 30,907 (12,158 ) 2,750 4,698 26,197 Charge-offs (523 ) (396 ) (1,441 ) (1,379 ) (3,739 ) Recoveries 347 101 225 443 1,116 Net charge-offs (176 ) (295 ) (1,216 ) (936 ) (2,623 ) Balance, March 31, 2020 $ 76,327 $ 141,022 $ 7,817 $ 18,029 $ 243,195 Activity in the allowance for credit losses for the three months ended March 31, 2019 was as follows: (In thousands) Commercial Real Estate Credit Card Other Consumer and Other Total Three Months Ended March 31, 2019 Balance, beginning of period $ 20,514 $ 29,838 $ 3,923 $ 2,419 $ 56,694 Provision for credit losses 1,874 5,307 898 1,206 9,285 Charge-offs (3,152 ) (417 ) (1,142 ) (1,553 ) (6,264 ) Recoveries 158 142 240 300 840 Net charge-offs (2,994 ) (275 ) (902 ) (1,253 ) (5,424 ) Balance, March 31, 2019 $ 19,394 $ 34,870 $ 3,919 $ 2,372 $ 60,555 A change in forecast methodology, as well as the composition of the loans resulted in a negative provision in the real estate-construction and development loan segment during the first quarter of 2020. Under the current stressed economic conditions, the Company’s forecast of expected losses in the construction and development segment no longer produced a forecast that was considered reasonable and supportable. As such, management adjusted the forecast methodology of this segment to better align with management’s expectation of loss under the modeled economic conditions. The other categories saw increases in the provision related to increased concern over the economic stresses related to COVID-19, as well as increased specific provisions of $22 million for two energy credits, previously identified as problem loans, both of which experienced further deterioration during the first quarter of 2020 and were negatively impacted by the sharp decline in commodity pricing. Reserve for Unfunded Commitments In addition to the allowance for credit losses, the Company has established a reserve for unfunded commitments, classified in other liabilities. This reserve is maintained at a level management believes to be sufficient to absorb losses arising from unfunded loan commitments. The reserve for unfunded commitments as of March 31, 2020 and December 31, 2019 was $29.4 million and $8.4 million , respectively. The increase from year end was due to the adoption of CECL. The adequacy of the reserve for unfunded commitments is determined monthly based on methodology similar to the methodology for determining the allowance for credit losses. For the three months ended March 31, 2020 and 2019 , net adjustments to the reserve for unfunded commitments were a benefit of $3.0 million and an expense of $300,000 , respectively, and were included in other non-interest expense.

Right-Of-Use Lease Assets and L

Right-Of-Use Lease Assets and Lease Liabilities	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Right-Of-Use Lease Assets and Lease Liabilities	RIGHT-OF-USE LEASE ASSETS AND LEASE LIABILITIES As of the first quarter 2019, the Company accounts for its leases in accordance with ASC Topic 842, Leases , which requires recognition of most leases, including operating leases, with a term greater than 12 months on the balance sheet. At lease commencement, the lease contract is reviewed to determine whether the contract is a finance lease or an operating lease; a lease liability is recognized on a discounted basis, related to the Company’s obligation to make lease payments; and a right-of-use asset is also recognized related to the Company’s right to use, or control the use of, a specified asset for the lease term. The Company accounts for lease and non-lease components (such as taxes, insurance and common area maintenance costs) separately as such amounts are generally readily determinable under the lease contracts. Lease payments over the expected term are discounted using the Company’s FHLB advance rates for borrowings of similar term. If it is reasonably certain that a renewal or termination option will be exercised, the effects of such options are included in the determination of the expected lease term. Leases with an initial term of 12 months or less are not recorded on the balance sheet; the Company recognizes lease expense for these leases on a straight-line basis over the lease term. The Company’s leases are classified as operating leases with a term, including expected renewal or termination options, greater than one year, and are related to certain office facilities and office equipment. Right-of-use lease assets included in premises and equipment were $38.3 million and $40.7 million at March 31, 2020 and December 31, 2019 , respectively. Lease liabilities included in other liabilities were $38.4 million and $40.9 million at March 31, 2020 and December 31, 2019 , respectively. Other information related to the Company’s operating leases is presented in the table below: Three Months Ended 2020 2019 Operating lease cost $ 3,200,500 $ 3,434,900 Weighted average remaining lease term 8.41 years 9.29 years Weighted average discount rate 3.27 % 3.46 %

Premises and Equipment

Premises and Equipment	3 Months Ended
	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
Premises and Equipment	PREMISES AND EQUIPMENT Premises and equipment are stated at cost less accumulated depreciation and amortization. Total premises and equipment, net at March 31, 2020 and December 31, 2019 were as follows: (In thousands) March 31, 2020 December 31, 2019 Right-of-use lease assets $ 38,345 $ 40,675 Premises and equipment: Land 97,152 99,931 Buildings and improvements 307,324 309,290 Furniture, fixtures and equipment 102,342 99,343 Software 60,369 56,012 Construction in progress 7,285 6,998 Accumulated depreciation and amortization (127,827 ) (119,865 ) Total premises and equipment, net $ 484,990 $ 492,384

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill is tested annually, or more often than annually, if circumstances warrant, for impairment. If the implied fair value of goodwill is lower than its carrying amount, goodwill impairment is indicated, and goodwill is written down to its implied fair value. Subsequent increases in goodwill value are not recognized in the financial statements. Goodwill totaled $1.065 billion at March 31, 2020 and $1.056 billion at December 31, 2019 . During 2019, the Company recorded $131.3 million and $78.5 million of goodwill as a result of its acquisitions of Landrum and Reliance, respectively. During the first quarter of 2020, goodwill increased $9.5 million related to the continued assessment of the fair value and assumed tax position of the Landrum acquisition. Goodwill impairment was neither indicated nor recorded during the three months ended March 31, 2020 or the year ended December 31, 2019 . During the first quarter 2020, the Company’s share price began to decline as the markets in the United States responded to the global COVID-19 pandemic. As a result of the economic decline, the effect on share price and other factors, the Company performed an interim goodwill impairment qualitative assessment and concluded that it is more likely-than-not that the fair value of goodwill continues to exceed its carrying value and therefore, goodwill is not impaired. Core deposit premiums represent the value of the relationships that acquired banks had with their deposit customers and are amortized over periods ranging from 10 years to 15 years and are periodically evaluated, at least annually, as to the recoverability of their carrying value. Other intangible assets represent the value of other acquired relationships, including relationships with trust and wealth management customers, and are being amortized over various periods ranging from 10 years to 15 years . Changes in the carrying amount and accumulated amortization of the Company’s core deposit premiums and other intangible assets at March 31, 2020 and December 31, 2019 were as follows: (In thousands) March 31, 2020 December 31, 2019 Core deposit premiums: Balance, beginning of year $ 111,808 $ 79,807 Acquisitions (1) — 42,695 Disposition of intangible asset (2) (1,841 ) — Amortization (3,070 ) (10,694 ) Balance, end of period 106,897 111,808 Books of business and other intangibles: Balance, beginning of year 15,532 11,527 Acquisitions (3) — 5,116 Disposition of intangible asset (413 ) — Amortization (343 ) (1,111 ) Balance, end of period 14,776 15,532 Total other intangible assets, net $ 121,673 $ 127,340 _________________________ (1) Core deposit premiums of $24.3 million and $18.4 million were recorded during 2019 as part of the Landrum and Reliance acquisitions, respectively. See Note 2, Acquisitions, for additional information on acquisitions completed in 2019. (2) Consisting of an adjustment for the premium on certain deposit liabilities related to the sale of the Texas Branches. (3) The Company recorded $5.1 million during 2019 primarily related to the wealth management operations acquired from Landrum. See Note 2, Acquisitions, for additional information on acquisitions completed in 2019. The carrying basis and accumulated amortization of the Company’s other intangible assets at March 31, 2020 and December 31, 2019 were as follows: (In thousands) March 31, 2020 December 31, 2019 Core deposit premiums: Gross carrying amount $ 146,838 $ 148,679 Accumulated amortization (39,941 ) (36,871 ) Core deposit premiums, net 106,897 111,808 Books of business and other intangibles: Gross carrying amount 19,938 20,350 Accumulated amortization (5,162 ) (4,818 ) Books of business and other intangibles, net 14,776 15,532 Total other intangible assets, net $ 121,673 $ 127,340 The Company’s estimated remaining amortization expense on other intangible assets as of March 31, 2020 is as follows: (In thousands) Year Amortization Expense Remainder of 2020 $ 10,120 2021 13,436 2022 13,384 2023 13,101 2024 12,199 Thereafter 59,433 Total $ 121,673

Time Deposits

Time Deposits	3 Months Ended
	Mar. 31, 2020
Banking and Thrift [Abstract]
Time Deposits	TIME DEPOSITS Time deposits included approximately $2.14 billion and $2.15 billion of certificates of deposit of $100,000 or more, at March 31, 2020 , and December 31, 2019 , respectively. Of this total approximately $1.1 billion and $837.3 million of certificates of deposit were over $250,000 at March 31, 2020 and December 31, 2019 , respectively.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The provision for income taxes is comprised of the following components for the periods indicated below: Three Months Ended (In thousands) 2020 2019 Income taxes currently payable $ 22,280 $ 10,317 Deferred income taxes (1,586 ) 2,081 Provision for income taxes $ 20,694 $ 12,398 The tax effects of temporary differences between the tax basis of assets and liabilities and their financial reporting amounts that give rise to deferred income tax assets and liabilities, and their approximate tax effects, are as follows: (In thousands) March 31, 2020 December 31, 2019 Deferred tax assets: Loans acquired $ 16,606 $ 20,783 Allowance for credit losses 60,678 16,732 Valuation of foreclosed assets 2,636 2,626 Tax NOLs from acquisition 17,467 18,118 Deferred compensation payable 2,866 2,750 Accrued equity and other compensation 5,914 6,677 Acquired securities — 3,393 Right-of-use lease liability 9,646 10,221 Allowance for unfunded commitments 7,376 — Other 5,414 7,886 Gross deferred tax assets 128,603 89,186 Deferred tax liabilities: Goodwill and other intangible amortization (40,378 ) (41,221 ) Accumulated depreciation (36,731 ) (36,554 ) Right-of-use lease asset (9,620 ) (10,176 ) Unrealized gain on available-for-sale securities (11,725 ) (3,720 ) Deferred loan fees and costs (2,994 ) (3,018 ) Acquired securities (771 ) — Other (5,332 ) (4,633 ) Gross deferred tax liabilities (107,551 ) (99,322 ) Net deferred tax asset (liability) $ 21,052 $ (10,136 ) A reconciliation of income tax expense at the statutory rate to the Company’s actual income tax expense is shown for the periods indicated below: Three Months Ended (In thousands) 2020 2019 Computed at the statutory rate (21%) $ 20,560 $ 12,620 Increase (decrease) in taxes resulting from: State income taxes, net of federal tax benefit 2,063 1,345 Discrete items related to ASU 2016-09 26 (26 ) Tax exempt interest income (1,421 ) (961 ) Tax exempt earnings on BOLI (319 ) (179 ) Federal tax credits (1,034 ) (729 ) Other differences, net 819 328 Actual tax provision $ 20,694 $ 12,398 The Company follows ASC Topic 740, Income Taxes , which prescribes a recognition threshold and a measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Benefits from tax positions should be recognized in the financial statements only when it is more likely than not that the tax position will be sustained upon examination by the appropriate taxing authority that would have full knowledge of all relevant information. A tax position that meets the more-likely-than-not recognition threshold is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. Tax positions that previously failed to meet the more-likely-than-not recognition threshold should be recognized in the first subsequent financial reporting period in which that threshold is met. Previously recognized tax positions that no longer meet the more-likely-than-not recognition threshold should be derecognized in the first subsequent financial reporting period in which that threshold is no longer met. ASC Topic 740 also provides guidance on the accounting for and disclosure of unrecognized tax benefits, interest and penalties. The Company has no history of expiring net operating loss carryforwards and is projecting significant pre-tax and financial taxable income in future years. The Company expects to fully realize its deferred tax assets in the future. The amount of unrecognized tax benefits may increase or decrease in the future for various reasons including adding amounts for current tax year positions, expiration of open income tax returns due to the statutes of limitation, changes in management’s judgment about the level of uncertainty, status of examinations, litigation and legislative activity and the addition or elimination of uncertain tax positions. Section 382 of the Internal Revenue Code imposes an annual limit on the ability of a corporation that undergoes an “ownership change” to use its U.S. net operating losses to reduce its tax liability. The Company has engaged in two tax-free reorganization transactions in which acquired net operating losses are limited pursuant to Section 382. In total, approximately $80.9 million of federal net operating losses subject to the IRC Section 382 annual limitation are expected to be utilized by the Company, of which $49.5 million is related to the Reliance acquisition that closed during second quarter 2019. All of the acquired Reliance net operating losses are expected to be fully utilized by 2027, with the remaining acquired net operating loss carryforwards expected to be fully utilized by 2036. The Company files income tax returns in the U.S. federal jurisdiction. The Company’s U.S. federal income tax returns are open and subject to examinations from the 2016 tax year and forward. The Company’s various state income tax returns are generally open from the 2016 and later tax return years based on individual state statute of limitations.

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase	3 Months Ended
	Mar. 31, 2020
Banking and Thrift [Abstract]
Securities Sold Under Agreements to Repurchase	SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE The Company utilizes securities sold under agreements to repurchase to facilitate the needs of its customers and to facilitate secured short-term funding needs. Securities sold under agreements to repurchase are stated at the amount of cash received in connection with the transaction. The Company monitors collateral levels on a continuous basis. The Company may be required to provide additional collateral based on the fair value of the underlying securities. Securities pledged as collateral under repurchase agreements are maintained with the Company’s safekeeping agents. The gross amount of recognized liabilities for repurchase agreements was $334.1 million and $133.2 million at March 31, 2020 and December 31, 2019 , respectively. The remaining contractual maturity of the securities sold under agreements to repurchase in the consolidated balance sheets as of March 31, 2020 and December 31, 2019 is presented in the following tables. Remaining Contractual Maturity of the Agreements (In thousands) Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total March 31, 2020 Repurchase agreements: U.S. Government agencies $ 334,064 $ — $ — $ — $ 334,064 December 31, 2019 Repurchase agreements: U.S. Government agencies $ 133,220 $ — $ — $ — $ 133,220

Other Borrowings and Subordinat

Other Borrowings and Subordinated Notes and Debentures	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Other Borrowings and Subordinated Notes and Debentures	OTHER BORROWINGS AND SUBORDINATED NOTES AND DEBENTURES Debt at March 31, 2020 and December 31, 2019 consisted of the following components: (In thousands) March 31, 2020 December 31, 2019 Other Borrowings FHLB advances, net of discount, due 2020 to 2034, 0.23% to 7.37% secured by real estate loans $ 1,362,295 $ 1,262,691 Other long-term debt 34,534 34,908 Total other borrowings 1,396,829 1,297,599 Subordinated Notes and Debentures Subordinated notes payable, due 4/1/2028, fixed-to-floating rate (fixed rate of 5.00% through 3/31/2023, floating rate of 2.15% above the three month LIBOR rate, reset quarterly) 330,000 330,000 Trust preferred securities, net of discount, due 9/15/2037, floating rate of 1.37% above the three month LIBOR rate, reset quarterly 10,310 10,310 Trust preferred securities, net of discount, due 6/6/2037, floating rate of 1.57% above the three month LIBOR rate, reset quarterly, callable without penalty 10,310 10,310 Trust preferred securities, due 12/15/2035, floating rate of 1.45% above the three month LIBOR rate, reset quarterly, callable without penalty 6,702 6,702 Trust preferred securities, net of discount, due 6/15/2037, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty 25,054 25,015 Trust preferred securities, net of discount, due 12/15/2036, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty 3,009 3,004 Other subordinated debentures, due 12/31/2036, floating rate of prime rate minus 1.1%, reset quarterly 5,927 5,927 Unamortized debt issuance costs (2,916 ) (3,008 ) Total subordinated notes and debentures 388,396 388,260 Total other borrowings and subordinated debt $ 1,785,225 $ 1,685,859 In March 2018, the Company issued $330.0 million in aggregate principal amount, of 5.00% Fixed-to-Floating Rate Subordinated Notes (“Notes”) at a public offering price equal to 100% of the aggregate principal amount of the Notes. The Company incurred $3.6 million in debt issuance costs related to the offering during March 2018. The Notes will mature on April 1, 2028 and will bear interest at an initial fixed rate of 5.00% per annum, payable semi-annually in arrears. From and including April 1, 2023 to, but excluding, the maturity date or the date of earlier redemption, the interest rate will reset quarterly to an annual interest rate equal to the then-current three month LIBOR rate plus 215 basis points, payable quarterly in arrears. The Notes will be subordinated in right of payment to the payment of the Company’s other existing and future senior indebtedness, including all of its general creditors. The Notes are obligations of the Company only and are not obligations of, and are not guaranteed by, any of its subsidiaries. The Company used a portion of the net proceeds from the sale of the Notes to repay certain outstanding indebtedness. The Notes qualify for Tier 2 capital treatment. The Company assumed subordinated debt of $33.9 million in connection with the Landrum acquisition in October 2019. At March 31, 2020 , the Company had $1.35 billion of FHLB advances outstanding with original or expected maturities of one year or less, of which $1.30 billion are FHLB Owns the Option (“FOTO”) advances. FOTO advances are a low cost, fixed-rate source of funding in return for granting to FHLB the flexibility to choose a termination date earlier than the maturity date. Typically, FOTO exercise dates follow a specified lockout period at the beginning of the term when FHLB cannot terminate the FOTO advance. If FHLB exercises its option to terminate the FOTO advance at one of the specified option exercise dates, there is no termination or prepayment fee, and replacement funding will be available at then-prevailing market rates, subject to FHLB’s credit and collateral requirements. The Company’s FOTO advances outstanding at March 31, 2020 have maturity dates of ten years to fifteen years with lockout periods that have expired and, as a result, are considered and monitored by the Company as short-term advances. The possibility of the FHLB exercising the options is analyzed by the Company along with the market expected rate outcome. The Company had total FHLB advances of $1.36 billion at March 31, 2020 , with approximately $2.1 billion of additional advances available from the FHLB. The FHLB advances are secured by mortgage loans and investment securities totaling approximately $5.4 billion at March 31, 2020 . The trust preferred securities are tax-advantaged issues that qualified for Tier 1 capital treatment until December 31, 2017, when the Company reached $15 billion in assets. They still qualify for inclusion as Tier 2 capital at March 31, 2020 . Distributions on these securities are included in interest expense on long-term debt. Each of the trusts is a statutory business trust organized for the sole purpose of issuing trust securities and investing the proceeds thereof in junior subordinated debentures of the Company, the sole asset of each trust. The preferred securities of each trust represent preferred beneficial interests in the assets of the respective trusts and are subject to mandatory redemption upon payment of the junior subordinated debentures held by the trust. The common securities of each trust are wholly-owned by the Company. Each trust’s ability to pay amounts due on the trust preferred securities is solely dependent upon the Company making payments on the related junior subordinated debentures. The Company’s obligations under the junior subordinated securities and other relevant trust agreements, in the aggregate, constitute a full and unconditional guarantee by the Company of each respective trust’s obligations under the trust securities issued by each respective trust. The Company’s long-term debt primarily includes subordinated debt and long-term FHLB advances with an original maturity of greater than one year. Aggregate annual maturities of long-term debt at March 31, 2020 , are as follows: Year (In thousands) Remainder of 2020 $ 2,946 2021 3,016 2022 2,187 2023 2,366 2024 2,446 Thereafter 422,264 Total $ 435,225

Contingent Liabilities

Contingent Liabilities	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Contingent Liabilities	CONTINGENT LIABILITIES The Company and/or its subsidiaries have various unrelated legal proceedings, which, in the aggregate, are not expected to have a material adverse effect on the financial position of the Company and its subsidiaries.

Capital Stock

Capital Stock	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Capital Stock	CAPITAL STOCK On February 27, 2009, at a special meeting, the Company’s shareholders approved an amendment to the Articles of Incorporation to establish 40,040,000 authorized shares of preferred stock, $0.01 par value. The aggregate liquidation preference of all shares of preferred stock cannot exceed $80,000,000 . On February 12, 2019, the Company filed its Amended and Restated Articles of Incorporation (“February Amended Articles”) with the Arkansas Secretary of State. The February Amended Articles classified and designated three series of preferred stock out of the Corporation’s authorized preferred stock: Series A Preferred Stock, Par Value $0.01 Per Share (having 40,000 authorized shares); Series B Preferred Stock, Par Value $0.01 Per Share (having 2,000.02 authorized shares); and 7% Perpetual Convertible Preferred Stock, Par Value $0.01 Per Share, Series C (having 140 authorized shares). On October 29, 2019, the Company filed its Amended and Restated Articles of Incorporation (“October Amended Articles”) with the Arkansas Secretary of State. The October Amended Articles classified and designated Series D Preferred Stock, Par Value $0.01 Per Share, out of the Company’s authorized preferred stock. The October Amended Articles also canceled the Company’s 7% Perpetual Convertible Preferred Stock, Par Value $0.01 Per Share, Series C Preferred Stock, of which no shares were ever issued or outstanding. On July 23, 2012, the Company approved a stock repurchase program which authorized the repurchase of up to 1,700,000 shares of common stock. On October 22, 2019, the Company announced a new stock repurchase program (“Program”) that replaced the stock repurchase program approved on July 23, 2012, under which the Company may repurchase up to $60,000,000 of its Class A common stock currently issued and outstanding. On March 5, 2020, the Company announced an amendment to the Program that increased the maximum amount that may be repurchased under the Program from $60,000,000 to $180,000,000 . The Program will terminate on October 31, 2021 (unless terminated sooner). Under the Program, the Company may repurchase shares of its common stock through open market and privately negotiated transactions or otherwise. The timing, pricing, and amount of any repurchases under the Program will be determined by the Company’s management at its discretion based on a variety of factors, including, but not limited to, trading volume and market price of the Company’s common stock, corporate considerations, the Company’s working capital and investment requirements, general market and economic conditions, and legal requirements. The Program does not obligate the Company to repurchase any common stock and may be modified, discontinued, or suspended at any time without prior notice. The Company anticipates funding for this Program to come from available sources of liquidity, including cash on hand and future cash flow. During the three months ended March 31, 2020 , the Company repurchased 4,922,336 shares at an average price of $18.96 under the Program. No shares have been repurchased since March 31, 2020 . Market conditions and the Company’s capital needs will drive decisions regarding additional, future stock repurchases. The Company had no repurchases of its common stock during the three month period ended March 31, 2019 .

Undivided Profits

Undivided Profits	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Undivided Profits	UNDIVIDED PROFITS Simmons Bank is subject to legal limitations on dividends that can be paid to the parent company without prior approval of the applicable regulatory agencies. The approval of the Commissioner of the Arkansas State Bank Department is required if the total of all dividends declared by an Arkansas state bank in any calendar year exceeds seventy-five percent ( 75% ) of the total of its net profits, as defined, for that year combined with seventy-five percent ( 75% ) of its retained net profits of the preceding year. At March 31, 2020 , Simmons Bank had approximately $222.5 million available for payment of dividends to the Company, without prior regulatory approval. The risk-based capital guidelines of the Federal Reserve Board and the Arkansas State Bank Department include the definitions for (1) a well-capitalized institution, (2) an adequately-capitalized institution, and (3) an undercapitalized institution. Under the Basel III Rules effective January 1, 2015, the criteria for a well-capitalized institution are: a 5% “Tier l leverage capital” ratio, an 8% “Tier 1 risk-based capital” ratio, 10% “total risk-based capital” ratio; and a 6.5% “common equity Tier 1 (CET1)” ratio. The Company and its subsidiary bank, Simmons Bank, must hold a capital conservation buffer composed of CET1 capital above its minimum risk-based capital requirements. The implementation of the capital conservation buffer began on January 1, 2016, at the 0.625% level and was phased in over a four year period (increasing by that amount on each subsequent January 1 until it reached 2.5% on January 1, 2019). As of March 31, 2020 , the Company and Simmons Bank met all capital adequacy requirements under the Basel III Capital Rules. The Company’s CET1 ratio was 11.10% at March 31, 2020

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION The Company’s Board of Directors has adopted various stock-based compensation plans. The plans provide for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and performance stock units. Pursuant to the plans, shares are reserved for future issuance by the Company upon exercise of stock options or awards of stock appreciation rights, stock awards or units granted to directors, officers and other key employees. The table below summarizes the transactions under the Company’s active stock-based compensation plans for the three months ended March 31, 2020 : Stock Options Outstanding Non-vested Stock Awards Outstanding Non-vested Stock Units Outstanding (Shares in thousands) Number of Shares Weighted Average Exercise Price Number of Shares Weighted Average Grant-Date Fair Value Number of Shares Weighted Average Grant-Date Fair Value Balance, January 1, 2020 692 $ 22.46 21 $ 23.19 1,152 $ 26.79 Granted — — — — 425 23.26 Stock options exercised (1 ) 10.71 — — — — Stock awards/units vested (earned) — — (4 ) 20.88 (351 ) 26.35 Forfeited/expired — — — — (42 ) 27.01 Balance, March 31, 2020 691 $ 22.48 17 $ 23.75 1,184 $ 25.64 Exercisable, March 31, 2020 691 $ 22.48 The following table summarizes information about stock options under the plans outstanding at March 31, 2020 : Options Outstanding Options Exercisable Range of Exercise Prices Number of Shares (In thousands) Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price Number of Shares (In thousands) Weighted Average Exercise Price $ 9.46 — $ 9.46 1 1.80 $9.46 1 $9.46 10.65 — 10.65 3 2.83 10.65 3 10.65 20.29 — 20.29 71 3.68 20.29 71 20.29 20.36 — 20.36 2 4.63 20.36 2 20.36 22.20 — 22.20 74 3.88 22.20 74 22.20 22.75 — 22.75 436 4.39 22.75 436 22.75 23.51 — 23.51 97 4.82 23.51 97 23.51 24.07 — 24.07 7 5.46 24.07 7 24.07 $ 9.46 — $ 24.07 691 4.32 $22.48 691 $22.48 The table below summarizes the Company’s performance stock unit activity for the three months ended March 31, 2020 : (In thousands) Performance Stock Units Non-vested, January 1, 2020 199 Granted 116 Vested (earned) (80 ) Forfeited (11 ) Non-vested, March 31, 2020 224 Stock-based compensation expense was $4,506,000 and $3,084,000 during the three months ended March 31, 2020 and 2019 , respectively. Stock-based compensation expense is recognized ratably over the requisite service period for all stock-based awards. There was no unrecognized stock-based compensation expense related to stock options at March 31, 2020 . Unrecognized stock-based compensation expense related to non-vested stock awards and stock units was $24,697,000 at March 31, 2020 . At such date, the weighted-average period over which this unrecognized expense is expected to be recognized was 2.2 years . The intrinsic value of stock options outstanding and stock options exercisable at March 31, 2020 was $33,000 . Aggregate intrinsic value represents the difference between the Company’s closing stock price on the last trading day of the period, which was $18.40 as of March 31, 2020 , and the exercise price multiplied by the number of options outstanding. The total intrinsic value of stock options exercised during the three months ended March 31, 2020 and March 31, 2019 , was $8,000 and $6,000 , respectively. The fair value of the Company’s employee stock options granted is estimated on the date of grant using the Black-Scholes option-pricing model. This model requires the input of highly subjective assumptions, changes to which can materially affect the fair value estimate. There were no stock options granted during the three months ended March 31, 2020 and 2019 .

Earnings Per Share ("EPS")

Earnings Per Share ("EPS")	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share (EPS)	EARNINGS PER SHARE (“EPS”) Basic EPS is computed by dividing reported net income available to common stockholders by weighted average number of common shares outstanding during each period. Diluted EPS is computed by dividing reported net income available to common stockholders by the weighted average common shares and all potential dilutive common shares outstanding during the period. The computation of earnings per share is as follows: Three Months Ended (In thousands, except per share data) 2020 2019 Net income available to common stockholders $ 77,223 $ 47,695 Average common shares outstanding 112,888 92,520 Average potential dilutive common shares 249 351 Average diluted common shares 113,137 92,871 Basic earnings per share $ 0.68 $ 0.52 Diluted earnings per share $ 0.68 $ 0.51 There were 614,100 stock options excluded from the three months ended March 31, 2020 earnings per share calculation due to the average market price exceeding the related exercise prices. There were no stock options excluded from the earnings per share calculation for the three months ended March 31, 2019 due to the related exercise price exceeding the average market price.

Additional Cash Flow Informatio

Additional Cash Flow Information	3 Months Ended
	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Additional Cash Flow Information	ADDITIONAL CASH FLOW INFORMATION The following is a summary of the Company’s additional cash flow information: Three Months Ended (In thousands) 2020 2019 Interest paid $ 39,388 $ 38,047 Income taxes paid (refunded) 92 (54 ) Transfers of loans to foreclosed assets held for sale 508 569 Transfers of premises to foreclosed assets and other real estate owned 3,120 — Right-of-use lease assets obtained in exchange for lessee operating lease liabilities (adoption of ASU 2016-02) — 32,757 Transfers of loans to other assets held for sale 114,925 — Transfers of deposits to other liabilities held for sale 58,405 —

Other Income and Other Operatin

Other Income and Other Operating Expenses	3 Months Ended
	Mar. 31, 2020
Other Income and Expenses [Abstract]
Other Income and Other Operating Expenses	OTHER INCOME AND OTHER OPERATING EXPENSES Other income for the three months ended March 31, 2020 was $12.8 million which included the $5.9 million gain on the Texas Branch Sale. Other income for the three months ended March 31, 2019 was $4.2 million . Other operating expenses consisted of the following: Three Months Ended (In thousands) 2020 2019 Professional services $ 5,829 $ 4,323 Postage 2,236 1,726 Telephone 2,185 1,619 Credit card expense 4,382 3,860 Marketing 4,385 3,057 Software and technology 6,415 4,496 Operating supplies 936 618 Amortization of intangibles 3,413 2,641 Branch right sizing expense 238 45 Other expense 8,769 7,677 Total other operating expenses $ 38,788 $ 30,062

Certain Transactions

Certain Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Certain Transactions	CERTAIN TRANSACTIONS From time to time, the Company and its subsidiaries have made loans, other extensions of credit, and vendor contracts to directors, officers, their associates and members of their immediate families. Additionally, some directors, officers and their associates and members of their immediate families have placed deposits with the Company’s subsidiary bank, Simmons Bank. Such loans and other extensions of credit, deposits and vendor contracts (which were not material) were made in the ordinary course of business, on substantially the same terms (including interest rates and collateral) as those prevailing at the time for comparable transactions with unrelated persons or through a competitive bid process. Further, in management’s opinion, these extensions of credit did not involve more than normal risk of collectability or present other unfavorable features.

Commitments and Credit Risk

Commitments and Credit Risk	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Credit Risk	COMMITMENTS AND CREDIT RISK The Company grants agri-business, commercial and residential loans to customers primarily throughout Arkansas, Colorado, Illinois, Kansas, Missouri, Oklahoma, Tennessee and Texas, along with credit card loans to customers throughout the United States. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since a portion of the commitments may expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. Each customer’s creditworthiness is evaluated on a case-by-case basis. The amount of collateral obtained, if deemed necessary, is based on management’s credit evaluation of the counterparty. Collateral held varies, but may include accounts receivable, inventory, property, plant and equipment, commercial real estate and residential real estate. At March 31, 2020 , the Company had outstanding commitments to extend credit aggregating approximately $618,583,000 and $3,148,372,000 for credit card commitments and other loan commitments. At December 31, 2019 , the Company had outstanding commitments to extend credit aggregating approximately $634,788,000 and $3,991,931,000 for credit card commitments and other loan commitments, respectively. Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. Those guarantees are primarily issued to support public and private borrowing arrangements, including commercial paper, bond financing, and similar transactions. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loans to customers. The Company had total outstanding letters of credit amounting to $70,628,000 and $71,074,000 at March 31, 2020 , and December 31, 2019 , respectively, with terms ranging from 9 months to 15 years . At March 31, 2020 and December 31, 2019 , the Company had no deferred revenue under standby letter of credit agreements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS ASC Topic 820, Fair Value Measurements defines fair value, establishes a framework for measuring fair value and expands disclosures about fair value measurements. ASC Topic 820 defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The guidance also establishes a fair value hierarchy that requires the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. Topic 820 describes three levels of inputs that may be used to measure fair value: • Level 1 Inputs – Quoted prices in active markets for identical assets or liabilities. • Level 2 Inputs – Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities in active markets; quoted prices for similar assets or liabilities in markets that are not active; 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 Inputs – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and the Company’s creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. The Company’s valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes the Company’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the reported fair value amounts have not been comprehensively revalued since the presentation dates, and therefore, estimates of fair value after the balance sheet date may differ significantly from the amounts presented herein. A more detailed description of the valuation methodologies used for assets and liabilities measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. Following is a description of the inputs and valuation methodologies used for assets measured at fair value on a recurring basis and recognized in the accompanying consolidated balance sheets, as well as the general classification of such assets pursuant to the valuation hierarchy. Available-for-sale securities – Where quoted market prices are available in an active market, securities are classified within Level 1 of the valuation hierarchy. Level 1 securities would include highly liquid government bonds, mortgage products and exchange traded equities. Other securities classified as available-for-sale are reported at fair value utilizing Level 2 inputs. For these securities, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. In order to ensure the fair values are consistent with ASC Topic 820, the Company periodically checks the fair values by comparing them to another pricing source, such as Bloomberg. The availability of pricing confirms Level 2 classification in the fair value hierarchy. The third-party pricing service is subject to an annual review of internal controls (SSAE 16), which is made available for the Company’s review. In certain cases where Level 1 or Level 2 inputs are not available, securities are classified within Level 3 of the hierarchy. The Company’s investment in U.S. Treasury securities, if any, is reported at fair value utilizing Level 1 inputs. The remainder of the Company’s available-for-sale securities are reported at fair value utilizing Level 2 inputs. Derivative instruments – The Company’s derivative instruments are reported at fair value utilizing Level 2 inputs. The Company obtains fair value measurements from dealer quotes. Other assets and other liabilities held for sale – The Company’s other assets and other liabilities held for sale are reported at fair value utilizing Level 3 inputs. See Note 4, Other Assets and Other Liabilities Held for Sale. The following table sets forth the Company’s financial assets by level within the fair value hierarchy that were measured at fair value on a recurring basis as of March 31, 2020 and December 31, 2019 . Fair Value Measurements Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) March 31, 2020 Available-for-sale securities U.S. Treasury $ 424,989 $ 424,989 $ — $ — U.S. Government agencies 161,289 — 161,289 — Mortgage-backed securities 1,179,837 — 1,179,837 — State and political subdivisions 678,243 — 678,243 — Other securities 22,282 — 22,282 — Other assets held for sale 115,315 — — 115,315 Derivative asset 42,102 — 42,102 — Other liabilities held for sale (58,405 ) — — (58,405 ) Derivative liability (42,482 ) — (42,482 ) — December 31, 2019 Available-for-sale securities U.S. Treasury $ 449,729 $ 449,729 $ — $ — U.S. Government agencies 194,249 — 194,249 — Mortgage-backed securities 1,742,945 — 1,742,945 — States and political subdivisions 880,524 — 880,524 — Other securities 20,896 — 20,896 — Other assets held for sale 260,332 — — 260,332 Derivative asset 14,903 — 14,903 — Other liabilities held for sale (159,853 ) — — (159,853 ) Derivative liability (12,650 ) — (12,650 ) — Certain financial 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. Financial assets and liabilities measured at fair value on a nonrecurring basis include the following: Individually assessed loans (collateral-dependent) – When the Company has a specific expectation to initiate, or has initiated, foreclosure proceedings, and when the repayment of a loan is expected to be substantially dependent on the liquidation of underlying collateral, the relationship is deemed collateral-dependent. Fair value of the loan is determined by establishing an allowance for credit loss for any exposure based on the valuation of the underlying collateral. The valuation of the collateral is determined by either an independent third-party appraisal or other collateral analysis. Discounts can be made by the Company based upon the overall evaluation of the independent appraisal. Collateral-dependent loans are classified within Level 3 of the fair value hierarchy. Collateral values supporting the individually assessed loans are evaluated quarterly for updates to appraised values or adjustments due to non-current valuations. Foreclosed assets and other real estate owned – Foreclosed assets and other real estate owned are reported at fair value, less estimated costs to sell. At foreclosure, if the fair value, less estimated costs to sell, of the real estate acquired is less than the Company’s recorded investment in the related loan, a write-down is recognized through a charge to the allowance for credit losses. Additionally, valuations are periodically performed by management and any subsequent reduction in value is recognized by a charge to income. The fair value of foreclosed assets and other real estate owned is estimated using Level 3 inputs based on unobservable market data. The significant unobservable inputs (Level 3) used in the fair value measurement of collateral for collateral-dependent loans and foreclosed assets primarily relate to the specialized discounting criteria applied to the borrower’s reported amount of collateral. The amount of the collateral discount depends upon the condition and marketability of the collateral, as well as other factors which may affect the collectability of the loan. Management’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset. It is reasonably possible that a change in the estimated fair value for instruments measured using Level 3 inputs could occur in the future. As the Company’s primary objective in the event of default would be to liquidate the collateral to settle the outstanding balance of the loan, collateral that is less marketable would receive a larger discount. Mortgage loans held for sale – Mortgage loans held for sale are reported at fair value if, on an aggregate basis, the fair value of the loans is less than cost. In determining whether the fair value of loans held for sale is less than cost when quoted market prices are not available, the Company may consider outstanding investor commitments, discounted cash flow analyses with market assumptions or the fair value of the collateral if the loan is collateral dependent. Such loans are classified within either Level 2 or Level 3 of the fair value hierarchy. Where assumptions are made using significant unobservable inputs, such loans held for sale are classified as Level 3. At March 31, 2020 and December 31, 2019 , the aggregate fair value of mortgage loans held for sale exceeded their cost. Accordingly, no mortgage loans held for sale were marked down and reported at fair value. The following table sets forth the Company’s financial assets by level within the fair value hierarchy that were measured at fair value on a nonrecurring basis as of March 31, 2020 and December 31, 2019 . Fair Value Measurements Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) March 31, 2020 Individually assessed loans (1) (2) (collateral-dependent) $ 38,901 $ — $ — $ 38,901 Foreclosed assets and other real estate owned (1) 2,050 — — 2,050 December 31, 2019 Individually assessed loans (1) (2) (collateral-dependent) $ 49,190 $ — $ — $ 49,190 Foreclosed assets and other real estate owned (1) 18,798 — — 18,798 ________________________ (1) These amounts represent the resulting carrying amounts on the consolidated balance sheets for collateral-dependent loans and foreclosed assets and other real estate owned for which fair value re-measurements took place during the period. (2) Identified reserves of $27,131,000 and $1,297,000 were related to collateral-dependent loans for which fair value re-measurements took place during the periods ended March 31, 2020 and December 31, 2019 , respectively. ASC Topic 825, Financial Instruments , requires disclosure in annual and interim financial statements of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or nonrecurring basis. The following methods and assumptions were used to estimate the fair value of each class of financial instruments not previously disclosed. Cash and cash equivalents – The carrying amount for cash and cash equivalents approximates fair value (Level 1). Interest bearing balances due from banks – The fair value of interest bearing balances due from banks – time is estimated using a discounted cash flow calculation that applies the rates currently offered on deposits of similar remaining maturities (Level 2). Held-to-maturity securities – Fair values for held-to-maturity securities equal quoted market prices, if available, such as for highly liquid government bonds (Level 1). If quoted market prices are not available, fair values are estimated based on quoted market prices of similar securities. For these securities, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things (Level 2). In certain cases where Level 1 or Level 2 inputs are not available, securities are classified within Level 3 of the hierarchy. Loans – The fair value of loans is estimated by discounting the future cash flows, using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities. Additional factors considered include the type of loan and related collateral, variable or fixed rate, classification status, remaining term, interest rate, historical delinquencies, loan to value ratios, current market rates and remaining loan balance. The loans were grouped together according to similar characteristics and were treated in the aggregate when applying various valuation techniques. The discount rates used for loans were based on current market rates for new originations of similar loans. Estimated credit losses were also factored into the projected cash flows of the loans. The fair value of loans is estimated on an exit price basis incorporating the above factors (Level 3). Deposits – The fair value of demand deposits, savings accounts and money market deposits is the amount payable on demand at the reporting date (i.e., their carrying amount) (Level 2). The fair value of fixed-maturity time deposits is estimated using a discounted cash flow calculation that applies the rates currently offered for deposits of similar remaining maturities (Level 3). Federal Funds purchased, securities sold under agreement to repurchase and short-term debt – The carrying amount for Federal funds purchased, securities sold under agreement to repurchase and short-term debt are a reasonable estimate of fair value (Level 2). Other borrowings – For short-term instruments, the carrying amount is a reasonable estimate of fair value. For long-term debt, rates currently available to the Company for debt with similar terms and remaining maturities are used to estimate the fair value (Level 2). Subordinated debentures – The fair value of subordinated debentures is estimated using the rates that would be charged for subordinated debentures of similar remaining maturities (Level 2). Accrued interest receivable/payable – The carrying amounts of accrued interest approximated fair value (Level 2). Commitments to extend credit, letters of credit and lines of credit – The fair value of commitments is estimated using the fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements and the present creditworthiness of the counterparties. For fixed rate loan commitments, fair value also considers the difference between current levels of interest rates and the committed rates. The fair values of letters of credit and lines of credit are based on fees currently charged for similar agreements or on the estimated cost to terminate or otherwise settle the obligations with the counterparties at the reporting date. The fair value of a financial instrument is the current amount that would be exchanged between willing parties, other than in a forced liquidation. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company’s various financial instruments. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the instrument. The estimated fair values, and related carrying amounts, of the Company’s financial instruments are as follows: Carrying Fair Value Measurements (In thousands) Amount Level 1 Level 2 Level 3 Total March 31, 2020 Financial assets: Cash and cash equivalents $ 1,737,199 $ 1,737,199 $ — $ — $ 1,737,199 Interest bearing balances due from banks - time 4,309 — 4,309 — 4,309 Held-to-maturity securities 53,968 — 55,714 — 55,714 Mortgage loans held for sale 49,984 — — 49,984 49,984 Interest receivable 57,039 — 57,039 — 57,039 Loans, net 14,131,082 — — 14,160,286 14,160,286 Financial liabilities: Non-interest bearing transaction accounts 3,572,244 — 3,572,244 — 3,572,244 Interest bearing transaction accounts and savings deposits 8,840,678 — 8,840,678 — 8,840,678 Time deposits 3,146,811 — — 3,163,694 3,163,694 Federal funds purchased and securities sold under agreements to repurchase 377,859 — 377,859 — 377,859 Other borrowings 1,396,829 — 1,411,137 — 1,411,137 Subordinated notes and debentures 388,396 — 407,301 — 407,301 Interest payable 15,258 — 15,258 — 15,258 December 31, 2019 Financial assets: Cash and cash equivalents $ 996,623 $ 996,623 $ — $ — $ 996,623 Interest bearing balances due from banks - time 4,554 — 4,554 — 4,554 Held-to-maturity securities 40,927 — 41,855 — 41,855 Mortgage loans held for sale 58,102 — — 58,102 58,102 Interest receivable 62,707 — 62,707 — 62,707 Loans, net 14,357,460 — — 14,290,188 14,290,188 Financial liabilities: Non-interest bearing transaction accounts 3,741,093 — 3,741,093 — 3,741,093 Interest bearing transaction accounts and savings deposits 9,090,878 — 9,090,878 — 9,090,878 Time deposits 3,276,969 — — 3,270,333 3,270,333 Federal funds purchased and securities sold under agreements to repurchase 150,145 — 150,145 — 150,145 Other borrowings 1,297,599 — 1,298,011 — 1,298,011 Subordinated debentures 388,260 — 397,088 — 397,088 Interest payable 12,898 — 12,898 — 12,898 The fair value of commitments to extend credit, letters of credit and lines of credit is not presented since management believes the fair value to be insignificant.

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS The Company utilizes derivative instruments to manage exposure to various types of interest rate risk for itself and its customers within policy guidelines. Transactions should only be entered into with an associated underlying exposure. All derivative instruments are carried at fair value. Derivative contracts involve the risk of dealing with institutional derivative counterparties and their ability to meet contractual terms. Institutional counterparties must have an investment grade credit rating and be approved by the Company’s asset/liability management committee. In arranging these products for its customers, the Company assumes additional credit risk from the customer and from the dealer counterparty with whom the transaction is undertaken. Credit risk exists due to the default credit risk created in the exchange of the payments over a period of time. Credit exposure on interest rate swaps is limited to the net favorable value and interest payments of all swaps with each counterparty. Access to collateral in the event of default is reasonably assured. Therefore, credit exposure may be reduced by the amount of collateral pledged by the counterparty. Hedge Structures The Company will seek to enter derivative structures that most effectively address the risk exposure and structural terms of the underlying position being hedged. The term and notional principal amount of a hedge transaction will not exceed the term or principal amount of the underlying exposure. In addition, the Company will use hedge indices which are the same as, or highly correlated to, the index or rate on the underlying exposure. Derivative credit exposure is monitored on an ongoing basis for each customer transaction and aggregate exposure to each counterparty is tracked. The Company has set a maximum outstanding notional contract amount at 10% of the Company’s assets. Customer Risk Management Interest Rate Swaps The Company’s qualified loan customers have the opportunity to participate in its interest rate swap program for the purpose of managing interest rate risk on their variable rate loans with the Company. The Company enters into such agreements with customers, then offsetting agreements are executed between the Company and an approved dealer counterparty to minimize market risk from changes in interest rates. The counterparty contracts are identical to customer contracts in terms of notional amounts, interest rates, and maturity dates, except for a fixed pricing spread or fee paid to the Company by the dealer counterparty. These interest rate swaps carry varying degrees of credit, interest rate and market or liquidity risks. The fair value of these derivative instruments is recognized as either derivative assets or liabilities in the accompanying consolidated balance sheets. The Company has a limited number of swaps that are standalone without a similar agreement with the loan customer. The Company has entered into interest rate swap agreements that effectively convert the loan interest rate from floating rate based on LIBOR or Prime rate to a fixed rate for the customer. The Company has entered into offsetting agreements with dealer counterparties. The following table summarizes the fair values of loan derivative contracts recorded in the accompanying consolidated balance sheets. March 31, 2020 December 31, 2019 (In thousands) Notional Fair Value Notional Fair Value Derivative assets $ 440,119 $ 42,102 $ 401,969 $ 14,903 Derivative liabilities 449,613 42,482 387,075 12,650 Risk Participation Agreements The Company has a limited number of Risk Participation Agreement swaps, that are associated with loan participations, where the Company is not the counterparty to the interest rate swaps that are associated with the risk participation sold. The interest rate swap mark to market only impacts the Company if the swap is in a liability position to the counterparty and the customer defaults on payments to the counterparty. The notional amount of these contingent agreements is $52.7 million as of March 31, 2020 . Energy Hedging During 2019, the Company began providing energy derivative services to qualifying, high quality oil and gas borrowers for hedging purposes. The Company serves as an intermediary on energy derivative products between the Company’s borrowers and dealers. The Company will only enter into back-to-back trades, thus maintaining a balanced book between the dealer and the borrower. Energy hedging risk exposure to the Company’s customer increases as energy prices for crude oil and natural gas rise. As prices decrease, exposure to the exchange increases. These risks are mitigated by customer credit underwriting policies and establishing a predetermined hedge line for each borrower and by monitoring the exchange margin. The outstanding notional value as of March 31, 2020 for energy hedging Customer Sell to Company swaps were $10.7 million and the corresponding Company Sell to Dealer swaps were $10.7 million and the corresponding net fair value of the derivative asset and derivative liability was $531,400 .

Recent Events

Recent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Recent Events	RECENT EVENTS The coronavirus (COVID-19) pandemic has placed significant health, economic and other major pressure on the communities the Company serves, the United States and the entire world. In March 2020, Congress passed the CARES Act, which is designed to provide comprehensive relief to individuals and businesses following the unprecedented impact of the COVID-19 pandemic. The Company has implemented a number of procedures in response to the pandemic to support the safety and well being of its employees, customers and shareholders that continue through the date of filing this report. Some of the newly implemented procedures include: • Addressing the safety of the Company’s 240 branches, following local, state, and federal guidelines. In March, the Company announced the temporary closure of 52 branches and is focusing on the enhanced digital banking experience; • Holding regular executive and pandemic task force meetings to address issues that change rapidly; • Implementing business continuity plans to help ensure that customers have adequate access to banking services; • Providing extensions and deferrals to loan customers affected by COVID-19 provided such customers were not 30 days or more past due at December 31, 2019. Through May 5, 2020, the Company has completed or is in the process of modifying more than 4,300 loans totaling over $3.2 billion ; and • Participating in both appropriations of the CARES Act Paycheck Protection Program (“PPP”) that provides 100% federally guaranteed loans for small businesses to cover up to eight weeks of payroll costs and assist with mortgage interest, rent and utilities. Notably, these small business loans may be forgiven by the SBA if borrowers maintain their payrolls and satisfy certain other conditions during this crisis. Through May 5, 2020, the Company has completed over 7,600 applications and funded over $978 million of such loans. The Company continues to closely monitor this pandemic and expects to make future changes to respond to the pandemic as this situation continues to evolve. Further economic downturns accompanying this pandemic could result in increased deterioration in credit quality, past due loans, loans charge offs and collateral value declines, which could cause our results of operations and financial condition to be negatively impacted.

Preparation of Interim Financ_2

Preparation of Interim Financial Statements (Policies)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared based upon Securities and Exchange Commission (“SEC”) rules that permit reduced disclosures for interim periods. Certain information and footnote disclosures have been condensed or omitted in accordance with those rules and regulations. The accompanying consolidated balance sheet as of December 31, 2019 , was derived from audited financial statements. In the opinion of management, these financial statements reflect all adjustments that are necessary for a fair presentation of interim results of operations, including normal recurring accruals. Significant intercompany accounts and transactions have been eliminated in consolidation. The results for the interim periods are not necessarily indicative of results for the full year. For a more complete discussion of significant accounting policies and certain other information, this report should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 , which was filed with the SEC on February 27, 2020 . The preparation of financial statements, in accordance with accounting principles generally accepted in the United States (“US GAAP”), requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, income items and expenses and disclosure of contingent assets and liabilities. The estimates and assumptions used in the accompanying consolidated financial statements are based upon management’s evaluation of the relevant facts and circumstances as of the date of the consolidated financial statements and actual results may differ from these estimates. Such estimates include, but are not limited to, the Company’s allowance for credit losses.
Reclassification	Certain prior year amounts have been reclassified to conform to the current year financial statement presentation. These changes and reclassifications did not impact previously reported net income or comprehensive income.
Recently Adopted and Issued Accounting Standards	Recently Adopted Accounting Standards Fair Value Measurement Disclosures – In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), that eliminates, amends and adds disclosure requirements for fair value measurements. These amendments are part of FASB’s disclosure review project and they are expected to reduce costs for preparers while providing more decision-useful information for financial statement users. The eliminated disclosure requirements include the 1) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; 2) the policy of timing of transfers between levels of the fair value hierarchy; and 3) the valuation processes for Level 3 fair value measurements. Among other modifications, the amended disclosure requirements remove the term “at a minimum” from the phrase “an entity shall disclose at a minimum” to promote the appropriate exercise of discretion by entities and clarifies that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Under the new disclosure requirements, entities must disclose the changes in unrealized gains or losses included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. ASU 2018-13 did not have a material impact on the Company’s fair value disclosures. Credit Losses on Financial Instruments – In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which requires earlier measurement of credit losses, expands the range of information considered in determining expected credit losses and enhances disclosures. The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The amendments replace the incurred loss impairment methodology in current US GAAP with a methodology (the current expected credit losses, or “CECL”, methodology) that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The CECL methodology utilizes a lifetime “expected credit loss” measurement objective for the recognition of credit losses for loans, held-to-maturity debt securities and other receivables measured at amortized cost at the time the financial asset is originated or acquired. The allowance for credit losses is adjusted each period for changes in expected lifetime credit losses. This methodology replaces the multiple existing impairment methods in current guidance, which generally require that a loss be incurred before it is recognized. Within the life cycle of a loan or other financial asset, this new guidance will generally result in the earlier recognition of the provision for credit losses and the related allowance for credit losses than current practice. For available-for-sale debt securities that the Company intends to hold and where fair value is less than cost, credit-related impairment, if any, will be recognized through an allowance for credit losses and adjusted each period for changes in credit risk. The effective date for these amendments is for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. In preparation for implementation of ASU 2016-13, the Company formed a cross functional team that assessed its data and system needs and evaluated the potential impact of adopting the new guidance. The Company anticipated a significant change in the processes and procedures to calculate the loan losses, including changes in assumptions and estimates to consider expected credit losses over the life of the loan versus the prior accounting practice that utilized the incurred loss model. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was signed in to law by the President of the United States and allows the option to temporarily defer or suspend the adoption of ASU 2016-13. During the deferral, a registrant would continue to use the incurred loss model for the allowance for loan and lease losses and would be in accordance with US GAAP. The Company has not elected to temporarily defer the adoption of ASU 2016-13 and adopted the new standard as of January 1, 2020. Upon adoption, the Company recorded an additional allowance for credit losses on loans of approximately $151.4 million and an adjustment to the reserve for unfunded commitments recorded in other liabilities of $24.0 million . The Company also recorded an additional allowance for credit losses on investment securities of $742,000 . The impact at adoption was reflected as an adjustment to beginning retained earnings, net of income taxes, in the amount of $128.1 million . The significant impact to the Company’s allowance for credit losses at the date of adoption was driven by the substantial amount of loans acquired held by the Company. The Company had approximately one third of total loans categorized as acquired at the adoption date with very little reserve allocated to them due to the previous incurred loss impairment methodology. As such, the amount of the CECL adoption impact was greater on the Company when compared to a non-acquisitive bank. In December 2018, the Federal Reserve, Office of the Comptroller of the Currency and Federal Deposit Insurance Corporation (“FDIC”) (collectively, the “agencies”) issued a final rule revising regulatory capital rules in anticipation of the adoption of ASU 2016-13 that provided an option to phase in over a three year period on a straight line basis the day-one impact on earnings and tier one capital (the “CECL Transition Provision”). In March 2020 and in response to the COVID-19 pandemic, the agencies issued a new regulatory capital rule revising the CECL Transition Provision to delay the estimated impact on regulatory capital stemming from the implementation of ASU 2016-13. The rule provides banking organizations that implement CECL before the end of 2020 the option to delay for two years an estimate of CECL’s effect on regulatory capital, followed by a three-year transition period (the “2020 CECL Transition Provision”). The Company elected to apply the 2020 CECL Transition Provision. In connection with the adoption of ASU 2016-13, the Company revised certain accounting policies and implemented certain accounting policy elections. The revised accounting policies are described below: Allowance for Credit Losses - Held-to-Maturity (“HTM”) Securities - The Company measures expected credit losses on HTM securities on a collective basis by major security type with each type sharing similar risk characteristics. The estimate of expected credit losses considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. The Company has made the election to exclude accrued interest receivable on HTM securities from the estimate of credit losses and report accrued interest separately on the consolidated balance sheets. See Note 3, Investment Securities, for additional information related to the Company’s allowance for credit losses on HTM securities. Allowance for Credit Losses - Available-for-Sale (“AFS”) Securities - For AFS securities in an unrealized loss position, the Company first evaluates whether it intends to sell, or whether it is more likely than not that it will be required to sell, the security before recovery of its amortized cost basis. If either of these criteria regarding intent or requirement to sell is met, the AFS security amortized cost basis is written down to fair value through income. If the criteria is not met, the Company is required to assess whether the decline in fair value has resulted from credit losses or noncredit-related factors. If the assessment indicates a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists, and an allowance for credit loss is recorded through income as a component of provision for credit loss expense. If the assessment indicates that a credit loss does not exist, the Company records the decline in fair value through other comprehensive income, net of related income tax effects. The Company has made the election to exclude accrued interest receivable on AFS securities from the estimate of credit losses and report accrued interest separately on the consolidated balance sheets. Changes in the allowance for credit losses are recorded as provision for (or reversal of) credit loss expense. Losses are charged against the allowance when management believes the uncollectibility of an AFS security is confirmed or when either of the criteria regarding intent or requirement to sell is met. See Note 3, Investment Securities, for additional information related to the Company’s allowance for credit losses on AFS securities. Loans - Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at their amortized cost basis, which is the unpaid principal balance outstanding, net of unearned income, deferred loan fees and costs, premiums and discounts associated with acquisition date fair value adjustments on acquired loans, and any direct principal charge-offs. The Company has made a policy election to exclude accrued interest from the amortized cost basis of loans and report accrued interest separately from the related loan balance on the consolidated balance sheets. Further information regarding accounting policies related to past due loans, non-accrual loans, and troubled-debt restructurings is presented in Note 5, Loans and Allowance for Credit Losses. The Company used the prospective transition approach for financial assets purchased with credit deterioration (“PCD”) that were previously classified as purchased credit impaired (“PCI”) and accounted for under Accounting Standards Codification (“ASC”) 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality . The Company increased the allowance for credit losses by approximately $5.4 million at adoption for the assets previously identified as PCI. In accordance with ASU 2016-13, the Company did not reassess whether PCI assets met the criteria of PCD assets as of the date of adoption. Collateral Dependent Loans - Loans that do not share risk characteristics are evaluated on an individual basis. For collateral dependent financial assets where the Company has determined that foreclosure of the collateral is probable, or where the borrower is experiencing financial difficulty and the Company expects repayment of the financial asset to be provided substantially through the operation or sale of the collateral, the allowance for credit loss is measured based on the difference between the fair value of the collateral and the amortized cost basis of the asset as of the measurement date. When repayment is expected to be from the operation of the collateral, expected credit losses are calculated as the amount by which the amortized cost basis of the financial asset exceeds the present value of expected cash flows from the operation of the collateral. When repayment is expected to be from the sale of the collateral, expected credit losses are calculated as the amount by which the amortized costs basis of the financial asset exceeds the fair value of the underlying collateral less estimated cost to sell. The allowance for credit losses may be zero if the fair value of the collateral at the measurement date exceeds the amortized cost basis of the financial asset. Allowance For Credit Losses - Off-Balance-Sheet Credit Exposures - The allowance for credit losses on off-balance-sheet credit exposures is a liability account representing expected credit losses over the contractual period for which the Company is exposed to credit risk resulting from a contractual obligation to extend credit. No allowance for credit loss is recognized if the Company has the unconditional right to cancel the obligation. The allowance for credit loss is reported as a component of accrued interest and other liabilities in the consolidated balance sheets. Adjustments to the allowance are reported in the income statement as a component of other operating expenses. Recently Issued Accounting Standards Reference Rate Reform – In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides relief for companies preparing for discontinuation of interest rates such as the London Interbank Offered Rate (“LIBOR”). LIBOR is a benchmark interest rate referenced in a variety of agreements that are used by numerous entities. After 2021, banks will no longer be required to report information that is used to determine LIBOR. As a result, LIBOR could be discontinued. Other interest rates used globally could also be discontinued for similar reasons. ASU 2020-04 provides optional expedients and exceptions to contracts, hedging relationships and other transactions affected by reference rate reform. The main provisions for contract modifications include optional relief by allowing the modification as a continuation of the existing contract without additional analysis and other optional expedients regarding embedded features. Optional expedients for hedge accounting permits changes to critical terms of hedging relationships and to the designated benchmark interest rate in a fair value hedge and also provides relief for assessing hedge effectiveness for cash flow hedges. Companies are able to apply ASU 2020-04 immediately; however, the guidance will only be available for a limited time (generally through December 31, 2022). As of March 31, 2020 , the Company has not made any modifications to hedges or other instruments that reference an interest rate that is expected to be discontinued. Income Taxes – In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), that removes certain exceptions for investments, intraperiod allocations and interim calculations, and adds guidance to reduce complexity in accounting for income taxes. ASU 2019-12 introduces the following new guidance: i) guidance to evaluate whether a step-up in tax basis of goodwill relates to a business combination in which book goodwill was recognized or a separate transaction and ii) a policy election to not allocate consolidated income taxes when a member of a consolidated tax return is not subject to income tax. Additionally, ASU 2019-12 changes the following current guidance: i) making an intraperiod allocation, if there is a loss in continuing operations and gains outside of continuing operations, ii) determining when a deferred tax liability is recognized after an investor in a foreign entity transitions to or from the equity method of accounting, iii) accounting for tax law changes and year-to-date losses in interim periods, and iv) determining how to apply the income tax guidance to franchise taxes that are partially based on income. ASU 2019-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating all of the amendments in ASU 2019-12 and has not yet determined the impact of this new standard. There have been no other significant changes to the Company’s accounting policies from the 2019 Form 10-K. Presently, the Company is not aware of any other changes to the Accounting Standards Codification that will have a material impact on its present or future financial position or results of operations.
Income Taxes	The Company follows ASC Topic 740, Income Taxes , which prescribes a recognition threshold and a measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Benefits from tax positions should be recognized in the financial statements only when it is more likely than not that the tax position will be sustained upon examination by the appropriate taxing authority that would have full knowledge of all relevant information. A tax position that meets the more-likely-than-not recognition threshold is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. Tax positions that previously failed to meet the more-likely-than-not recognition threshold should be recognized in the first subsequent financial reporting period in which that threshold is met. Previously recognized tax positions that no longer meet the more-likely-than-not recognition threshold should be derecognized in the first subsequent financial reporting period in which that threshold is no longer met. ASC Topic 740 also provides guidance on the accounting for and disclosure of unrecognized tax benefits, interest and penalties. The Company has no history of expiring net operating loss carryforwards and is projecting significant pre-tax and financial taxable income in future years. The Company expects to fully realize its deferred tax assets in the future. The amount of unrecognized tax benefits may increase or decrease in the future for various reasons including adding amounts for current tax year positions, expiration of open income tax returns due to the statutes of limitation, changes in management’s judgment about the level of uncertainty, status of examinations, litigation and legislative activity and the addition or elimination of uncertain tax positions.

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Fair Value of Assets Acquired and Liabilities Assumed	A summary, at fair value, of the assets acquired and liabilities assumed in the Reliance transaction, as of the acquisition date, is as follows: (In thousands) Acquired from Reliance Fair Value Adjustments Fair Value Assets Acquired Cash and due from banks $ 25,693 $ — $ 25,693 Due from banks - time 502 — 502 Investment securities 287,983 (1,873 ) 286,110 Loans acquired 1,138,527 (41,657 ) 1,096,870 Allowance for loan losses (10,808 ) 10,808 — Foreclosed assets 11,092 (5,180 ) 5,912 Premises and equipment 32,452 (3,001 ) 29,451 Bank owned life insurance 39,348 — 39,348 Core deposit intangible — 18,350 18,350 Other assets 25,165 6,911 32,076 Total assets acquired $ 1,549,954 $ (15,642 ) $ 1,534,312 (In thousands) Acquired from Reliance Fair Value Adjustments Fair Value Liabilities Assumed Deposits: Non-interest bearing transaction accounts $ 108,845 $ (33 ) $ 108,812 Interest bearing transaction accounts and savings deposits 639,798 — 639,798 Time deposits 478,415 (1,758 ) 476,657 Total deposits 1,227,058 (1,791 ) 1,225,267 Securities sold under agreement to repurchase 14,146 — 14,146 Other borrowings 162,900 (5,500 ) 157,400 Accrued interest and other liabilities 8,185 268 8,453 Total liabilities assumed 1,412,289 (7,023 ) 1,405,266 Equity 137,665 (137,665 ) — Total equity assumed 137,665 (137,665 ) — Total liabilities and equity assumed $ 1,549,954 $ (144,688 ) $ 1,405,266 Net assets acquired 129,046 Purchase price 207,539 Goodwill $ 78,493 A summary, at fair value, of the assets acquired and liabilities assumed in the Landrum transaction, as of the acquisition date, is as follows: (In thousands) Acquired from Landrum Fair Value Adjustments Fair Value Assets Acquired Cash and due from banks $ 215,285 $ — $ 215,285 Due from banks - time 248 — 248 Investment securities 1,021,755 4,228 1,025,983 Loans acquired 2,049,137 (43,651 ) 2,005,486 Allowance for loan losses (22,736 ) 22,736 — Foreclosed assets 373 (183 ) 190 Premises and equipment 63,878 18,867 82,745 Bank owned life insurance 19,206 — 19,206 Goodwill 407 (407 ) — Core deposit intangible — 24,345 24,345 Other intangibles 412 4,704 5,116 Other assets 33,924 (13,401 ) 20,523 Total assets acquired $ 3,381,889 $ 17,238 $ 3,399,127 Liabilities Assumed Deposits: Non-interest bearing transaction accounts $ 716,675 $ — $ 716,675 Interest bearing transaction accounts and savings deposits 1,465,429 — 1,465,429 Time deposits 867,197 299 867,496 Total deposits 3,049,301 299 3,049,600 Other borrowings 10,055 — 10,055 Subordinated debentures 34,794 (877 ) 33,917 Accrued interest and other liabilities 31,057 (484 ) 30,573 Total liabilities assumed 3,125,207 (1,062 ) 3,124,145 Equity 256,682 (256,682 ) — Total equity assumed 256,682 (256,682 ) — Total liabilities and equity assumed $ 3,381,889 $ (257,744 ) $ 3,124,145 Net assets acquired 274,982 Purchase price 415,779 Goodwill $ 140,797

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	The amortized cost, fair value and allowance for credit losses of investment securities that are classified as HTM are as follows: (In thousands) Amortized Cost Allowance for Credit Losses Net Carrying Amount Gross Unrealized Gains Gross Unrealized (Losses) Estimated Fair Value Held-to-Maturity March 31, 2020 Mortgage-backed securities $ 27,121 $ — $ 27,121 $ 668 $ (1 ) $ 27,788 State and political subdivisions 26,082 (97 ) 25,985 981 (12 ) 26,954 Other securities 1,174 (312 ) 862 110 — 972 Total HTM $ 54,377 $ (409 ) $ 53,968 $ 1,759 $ (13 ) $ 55,714 (In thousands) Amortized Cost Allowance for Credit Losses Net Carrying Amount Gross Unrealized Gains Gross Unrealized (Losses) Estimated Fair Value December 31, 2019 Mortgage-backed securities $ 10,796 $ — $ 10,796 $ 71 $ (59 ) $ 10,808 State and political subdivisions 27,082 — 27,082 849 — 27,931 Other securities 3,049 — 3,049 67 — 3,116 Total HTM $ 40,927 $ — $ 40,927 $ 987 $ (59 ) $ 41,855
Debt Securities, Available-for-sale	The amortized cost, fair value and allowance for credit losses of investment securities that are classified as AFS are as follows: (In thousands) Amortized Allowance for Credit Losses Gross Unrealized Gross Unrealized Estimated Fair Available-for-sale March 31, 2020 U.S. Treasury $ 425,032 $ — $ — $ (43 ) $ 424,989 U.S. Government agencies 161,473 — 707 (891 ) 161,289 Mortgage-backed securities 1,150,878 — 32,068 (3,109 ) 1,179,837 State and political subdivisions 659,350 (95 ) 20,243 (1,255 ) 678,243 Other securities 21,765 (174 ) 866 (175 ) 22,282 Total AFS $ 2,418,498 $ (269 ) $ 53,884 $ (5,473 ) $ 2,466,640 December 31, 2019 U.S. Treasury $ 449,729 $ — $ 112 $ (112 ) $ 449,729 U.S. Government agencies 194,207 — 1,313 (1,271 ) 194,249 Mortgage-backed securities 1,738,584 — 8,510 (4,149 ) 1,742,945 State and political subdivisions 860,539 — 20,983 (998 ) 880,524 Other securities 20,092 — 822 (18 ) 20,896 Total AFS $ 3,263,151 $ — $ 31,740 $ (6,548 ) $ 3,288,343
Gross Unrealized Losses and Fair Value of Investments	The following table summarizes the Company’s AFS investments in an unrealized loss position for which an allowance for credit loss has not been recorded as of March 31, 2020 , aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position: Less Than 12 Months 12 Months or More Total (In thousands) Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Available-for-sale U.S. Treasury $ 424,989 $ (43 ) $ — $ — $ 424,989 $ (43 ) U.S. Government agencies — — 58,056 (891 ) 58,056 (891 ) Mortgage-backed securities 57,718 (1,318 ) 74,523 (1,791 ) 132,241 (3,109 ) State and political subdivisions 24,813 (1,157 ) 425 (4 ) 25,238 (1,161 ) Total AFS $ 507,520 $ (2,518 ) $ 133,004 $ (2,686 ) $ 640,524 $ (5,204 )
Debt Securities, Allowance for Credit Loss	The following table details activity in the allowance for credit losses by investment security type for the three months ended March 31, 2020 on the Company’s HTM and AFS securities held. (In thousands) State and Political Subdivisions Other Securities Total Held-to-Maturity Balance, January 1, 2020 $ — $ — $ — Impact of ASU 2016-13 adoption 58 311 369 Provision for credit loss expense 39 1 40 Balance, March 31, 2020 $ 97 $ 312 $ 409 Available-for-sale Balance, January 1, 2020 $ — $ — $ — Impact of ASU 2016-13 adoption 373 — 373 Credit losses on securities not previously recorded 44 174 218 Net increase (decrease) in allowance on previously impaired securities (322 ) — (322 ) Balance, March 31, 2020 $ 95 $ 174 $ 269
Debt Securities, Held-to-maturity, Credit Quality Indicator	The following table summarizes bond ratings for the Company’s HTM portfolio issued by state and political subdivisions and other securities as of March 31, 2020 : State and Political Subdivisions (In thousands) Not Guaranteed or Pre-Refunded Other Credit Enhancement or Insurance Pre-Refunded Total Other Securities Aaa/AAA $ 2,111 $ — $ — $ 2,111 $ — Aa/AA 12,596 6,203 285 19,084 — A 766 929 — 1,695 — Not Rated 2,323 370 499 3,192 1,174 Total $ 17,796 $ 7,502 $ 784 $ 26,082 $ 1,174
Income Earned on Securities	Income earned on securities for the three months ended March 31, 2020 and 2019 , is as follows: Three Months Ended (In thousands) 2020 2019 Taxable: Held-to-maturity $ 171 $ 438 Available-for-sale 12,581 11,520 Non-taxable: Held-to-maturity 72 1,162 Available-for-sale 6,119 3,161 Total $ 18,943 $ 16,281
Amortized Cost and Estimated Fair Value by Maturity of Securities	The amortized cost and estimated fair value by maturity of securities are shown in the following table. Securities are classified according to their contractual maturities without consideration of principal amortization, potential prepayments or call options. Accordingly, actual maturities may differ from contractual maturities. Held-to-Maturity Available-for-Sale (In thousands) Amortized Cost Fair Value Amortized Cost Fair Value One year or less $ 4,543 $ 4,563 $ 437,199 $ 437,187 After one through five years 15,414 15,769 34,541 34,889 After five through ten years 7,299 7,594 108,605 109,611 After ten years — — 686,714 703,839 Securities not due on a single maturity date 27,121 27,788 1,150,878 1,179,837 Other securities (no maturity) — — 561 1,277 Total $ 54,377 $ 55,714 $ 2,418,498 $ 2,466,640

Loans and Allowance for Loan _2

Loans and Allowance for Loan Losses (Tables)	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
Loan Portfolio	The various categories of loans are summarized as follows: (In thousands) March 31, 2020 December 31, 2019 Consumer: Credit cards $ 188,596 $ 204,802 Other consumer 267,870 249,195 Total consumer 456,466 453,997 Real Estate: Construction and development 2,024,118 2,248,673 Single family residential 2,343,543 2,414,753 Other commercial 6,466,104 6,358,514 Total real estate 10,833,765 11,021,940 Commercial: Commercial 2,314,472 2,451,119 Agricultural 191,535 191,525 Total commercial 2,506,007 2,642,644 Other 578,039 307,123 Total loans $ 14,374,277 $ 14,425,704
Nonaccrual Loans	The amortized cost basis of nonaccrual loans segregated by class of loans are as follows: (In thousands) March 31, 2020 December 31, 2019 Consumer: Credit cards $ 265 $ 382 Other consumer 2,111 1,705 Total consumer 2,376 2,087 Real estate: Construction and development 6,604 5,289 Single family residential 30,829 27,695 Other commercial 36,428 16,582 Total real estate 73,861 49,566 Commercial: Commercial 78,944 40,924 Agricultural 682 753 Total commercial 79,626 41,677 Total $ 155,863 $ 93,330
Past Due Loans	An age analysis of the amortized cost basis of past due loans, including nonaccrual loans, segregated by class of loans is as follows: (In thousands) Gross 30-89 Days Past Due 90 Days or More Past Due Total Past Due Current Total Loans 90 Days Past Due & Accruing March 31, 2020 Consumer: Credit cards $ 866 $ 325 $ 1,191 $ 187,405 $ 188,596 $ 115 Other consumer 4,540 1,131 5,671 262,199 267,870 — Total consumer 5,406 1,456 6,862 449,604 456,466 115 Real estate: Construction and development 2,713 5,013 7,726 2,016,392 2,024,118 — Single family residential 31,236 15,246 46,482 2,297,061 2,343,543 321 Other commercial 23,524 10,673 34,197 6,431,907 6,466,104 1 Total real estate 57,473 30,932 88,405 10,745,360 10,833,765 322 Commercial: Commercial 16,361 25,130 41,491 2,272,981 2,314,472 723 Agricultural 377 560 937 190,598 191,535 — Total commercial 16,738 25,690 42,428 2,463,579 2,506,007 723 Other — — — 578,039 578,039 — Total $ 79,617 $ 58,078 $ 137,695 $ 14,236,582 $ 14,374,277 $ 1,160 December 31, 2019 Consumer: Credit cards $ 848 $ 641 $ 1,489 $ 203,313 $ 204,802 $ 259 Other consumer 4,884 735 5,619 243,576 249,195 — Total consumer 5,732 1,376 7,108 446,889 453,997 259 Real estate: Construction and development 5,792 1,078 6,870 2,241,803 2,248,673 — Single family residential 26,318 13,789 40,107 2,374,646 2,414,753 597 Other commercial 7,645 6,450 14,095 6,344,419 6,358,514 — Total real estate 39,755 21,317 61,072 10,960,868 11,021,940 597 Commercial: Commercial 10,579 13,551 24,130 2,426,989 2,451,119 — Agricultural 1,223 456 1,679 189,846 191,525 — Total commercial 11,802 14,007 25,809 2,616,835 2,642,644 — Other — — — 307,123 307,123 — Total $ 57,289 $ 36,700 $ 93,989 $ 14,331,715 $ 14,425,704 $ 856
Impaired Financing Receivables	The following table presents information pertaining to impaired loans as of December 31, 2019 , in accordance with previous US GAAP prior to the adoption of ASU 2016-13. (In thousands) Unpaid Contractual Principal Balance Recorded Investment With No Allowance Recorded Investment With Allowance Total Recorded Investment Related Allowance Average Investment in Impaired Loans Interest Income Recognized December 31, 2019 Three Months Ended Consumer: Credit cards $ 382 $ 382 $ — $ 382 $ — $ 317 $ 30 Other consumer 1,537 1,378 — 1,378 — 1,857 13 Total consumer 1,919 1,760 — 1,760 — 2,174 43 Real estate: Construction and development 4,648 4,466 72 4,538 4 1,920 14 Single family residential 19,466 15,139 2,963 18,102 42 13,703 98 Other commercial 10,645 4,713 3,740 8,453 694 8,992 64 Total real estate 34,759 24,318 6,775 31,093 740 24,615 176 Commercial: Commercial 53,436 6,582 28,998 35,580 5,007 20,739 148 Agricultural 525 383 116 499 — 1,147 8 Total commercial 53,961 6,965 29,114 36,079 5,007 21,886 156 Total $ 90,639 $ 33,043 $ 35,889 $ 68,932 $ 5,747 $ 48,675 $ 375
Troubled Debt Restructuring	The following table presents a summary of TDRs segregated by class of loans. Accruing TDR Loans Nonaccrual TDR Loans Total TDR Loans (Dollars in thousands) Number Balance Number Balance Number Balance March 31, 2020 Real estate: Construction and development — $ — 1 $ 71 1 $ 71 Single-family residential 7 898 12 904 19 1,802 Other commercial 1 455 2 75 3 530 Total real estate 8 1,353 15 1,050 23 2,403 Commercial: Commercial 4 2,757 3 73 7 2,830 Total commercial 4 2,757 3 73 7 2,830 Total 12 $ 4,110 18 $ 1,123 30 $ 5,233 December 31, 2019 Real estate: Construction and development — $ — 1 $ 72 1 $ 72 Single-family residential 7 1,151 12 671 19 1,822 Other commercial 1 476 2 80 3 556 Total real estate 8 1,627 15 823 23 2,450 Commercial: Commercial 4 2,784 3 79 7 2,863 Total commercial 4 2,784 3 79 7 2,863 Total 12 $ 4,411 18 $ 902 30 $ 5,313
Loans by Credit Risk Ratings	The following table presents a summary of loans by credit quality indicator as of March 31, 2020 segregated by class of loans. Term Loans Amortized Cost Basis by Origination Year (In thousands) 2020 (YTD) 2019 2018 2017 2016 2015 and Prior Lines of Credit Amortized Cost Basis Lines of Credit Converted to Term Loans Amortized Cost Basis Total March 31, 2020 Consumer - credit cards Delinquency: 30-89 days past due $ — $ — $ — $ — $ — $ — $ 866 $ — $ 866 90+ days past due — — — — — — 325 — 325 Total consumer - credit cards — — — — — — 1,191 — 1,191 Consumer - other Delinquency: 30-89 days past due 47 1,109 636 1,188 1,182 251 128 — 4,541 90+ days past due — 147 97 446 203 60 178 — 1,131 Total consumer - other 47 1,256 733 1,634 1,385 311 306 — 5,672 Real estate - C&D Risk rating: 5 internal grade — 45 19 1,957 21 — — — 2,042 6 internal grade — 3,569 620 206 432 626 2,401 209 8,063 7 internal grade — — — — — — — — — Total real estate - C&D — 3,614 639 2,163 453 626 2,401 209 10,105 Real estate - SF residential Delinquency: 30-89 days past due 33 4,672 6,168 4,648 5,010 8,233 2,471 — 31,235 90+ days past due — 2,115 4,074 2,394 1,829 3,748 1,086 — 15,246 Total real estate - SF residential 33 6,787 10,242 7,042 6,839 11,981 3,557 — 46,481 Real estate - other commercial Risk rating: 5 internal grade 1,037 23,628 2,116 985 4,845 3,379 12,477 — 48,467 6 internal grade 2,728 16,060 17,211 4,369 6,860 20,059 37,552 1,037 105,876 7 internal grade — — — — — — — — — Total real estate - other commercial 3,765 39,688 19,327 5,354 11,705 23,438 50,029 1,037 154,343 Commercial Risk rating: 5 internal grade — 209 14 270 407 77 25,418 — 26,395 6 internal grade 16 11,925 6,994 16,480 1,264 764 54,993 743 93,179 7 internal grade — — — — — — — — — Total commercial 16 12,134 7,008 16,750 1,671 841 80,411 743 119,574 Commercial - agriculture Risk rating: 5 internal grade — 67 — 25 12 — 17 — 121 6 internal grade — 115 177 169 88 8 230 — 787 7 internal grade — — — — — — — — — Total commercial - agriculture — 182 177 194 100 8 247 — 908 Total $ 3,861 $ 63,661 $ 38,126 $ 33,137 $ 22,153 $ 37,205 $ 138,142 $ 1,989 $ 338,274 The following table presents a summary of loans by credit risk rating as of December 31, 2019 segregated by class of loans. (In thousands) Risk Rate 1-4 Risk Rate 5 Risk Rate 6 Risk Rate 7 Risk Rate 8 Total December 31, 2019 Consumer: Credit cards $ 204,161 $ — $ 641 $ — $ — $ 204,802 Other consumer 247,668 — 2,026 — — 249,694 Total consumer 451,829 — 2,667 — — 454,496 Real estate: Construction and development 2,229,019 70 7,735 — 37 2,236,861 Single family residential 2,394,284 6,049 41,601 130 — 2,442,064 Other commercial 6,068,425 69,745 67,429 — — 6,205,599 Total real estate 10,691,728 75,864 116,765 130 37 10,884,524 Commercial: Commercial 2,384,263 26,713 84,317 43 180 2,495,516 Agricultural 309,741 41 5,672 — — 315,454 Total commercial 2,694,004 26,754 89,989 43 180 2,810,970 Other 275,714 — — — — 275,714 Total $ 14,113,275 $ 102,618 $ 209,421 $ 173 $ 217 $ 14,425,704
Allowance for Loan Losses	The collateral securing these loans consist of commercial real estate properties, residential properties, other business assets, and secured energy production assets. (In thousands) Real Estate Collateral Energy Other Collateral Total Construction and development $ 3,078 $ — $ — $ 3,078 Single family residential 3,586 — — 3,586 Other commercial real estate 16,984 — — 16,984 Commercial — 43,573 8,449 52,022 Total $ 23,648 $ 43,573 $ 8,449 $ 75,670 The following table details activity in the allowance for credit losses by portfolio segment for loans for the three months ended March 31, 2020 . Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. (In thousands) Commercial Real Estate Credit Card Other Consumer and Other Total Three Months Ended March 31, 2020 Allowance for credit losses: Beginning balance, prior to adoption of CECL $ 22,863 $ 39,161 $ 4,051 $ 2,169 $ 68,244 Impact of CECL adoption 22,733 114,314 2,232 12,098 151,377 Provision for credit loss expense 30,907 (12,158 ) 2,750 4,698 26,197 Charge-offs (523 ) (396 ) (1,441 ) (1,379 ) (3,739 ) Recoveries 347 101 225 443 1,116 Net charge-offs (176 ) (295 ) (1,216 ) (936 ) (2,623 ) Balance, March 31, 2020 $ 76,327 $ 141,022 $ 7,817 $ 18,029 $ 243,195 Activity in the allowance for credit losses for the three months ended March 31, 2019 was as follows: (In thousands) Commercial Real Estate Credit Card Other Consumer and Other Total Three Months Ended March 31, 2019 Balance, beginning of period $ 20,514 $ 29,838 $ 3,923 $ 2,419 $ 56,694 Provision for credit losses 1,874 5,307 898 1,206 9,285 Charge-offs (3,152 ) (417 ) (1,142 ) (1,553 ) (6,264 ) Recoveries 158 142 240 300 840 Net charge-offs (2,994 ) (275 ) (902 ) (1,253 ) (5,424 ) Balance, March 31, 2019 $ 19,394 $ 34,870 $ 3,919 $ 2,372 $ 60,555

Right-Of-Use Lease Assets and_2

Right-Of-Use Lease Assets and Lease Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Components of Lease Expense and Supplemental Information	Other information related to the Company’s operating leases is presented in the table below: Three Months Ended 2020 2019 Operating lease cost $ 3,200,500 $ 3,434,900 Weighted average remaining lease term 8.41 years 9.29 years Weighted average discount rate 3.27 % 3.46 %

Premises and Equipment (Tables)

Premises and Equipment (Tables) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Right-of-use lease assets	$ 38,345	$ 40,675
Property, Plant and Equipment	Total premises and equipment, net at March 31, 2020 and December 31, 2019 were as follows: (In thousands) March 31, 2020 December 31, 2019 Right-of-use lease assets $ 38,345 $ 40,675 Premises and equipment: Land 97,152 99,931 Buildings and improvements 307,324 309,290 Furniture, fixtures and equipment 102,342 99,343 Software 60,369 56,012 Construction in progress 7,285 6,998 Accumulated depreciation and amortization (127,827 ) (119,865 ) Total premises and equipment, net $ 484,990 $ 492,384

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Changes in the carrying amount and accumulated amortization of the Company’s core deposit premiums and other intangible assets at March 31, 2020 and December 31, 2019 were as follows: (In thousands) March 31, 2020 December 31, 2019 Core deposit premiums: Balance, beginning of year $ 111,808 $ 79,807 Acquisitions (1) — 42,695 Disposition of intangible asset (2) (1,841 ) — Amortization (3,070 ) (10,694 ) Balance, end of period 106,897 111,808 Books of business and other intangibles: Balance, beginning of year 15,532 11,527 Acquisitions (3) — 5,116 Disposition of intangible asset (413 ) — Amortization (343 ) (1,111 ) Balance, end of period 14,776 15,532 Total other intangible assets, net $ 121,673 $ 127,340 _________________________ (1) Core deposit premiums of $24.3 million and $18.4 million were recorded during 2019 as part of the Landrum and Reliance acquisitions, respectively. See Note 2, Acquisitions, for additional information on acquisitions completed in 2019. (2) Consisting of an adjustment for the premium on certain deposit liabilities related to the sale of the Texas Branches. (3) The Company recorded $5.1 million during 2019 primarily related to the wealth management operations acquired from Landrum. See Note 2, Acquisitions, for additional information on acquisitions completed in 2019. The carrying basis and accumulated amortization of the Company’s other intangible assets at March 31, 2020 and December 31, 2019 were as follows: (In thousands) March 31, 2020 December 31, 2019 Core deposit premiums: Gross carrying amount $ 146,838 $ 148,679 Accumulated amortization (39,941 ) (36,871 ) Core deposit premiums, net 106,897 111,808 Books of business and other intangibles: Gross carrying amount 19,938 20,350 Accumulated amortization (5,162 ) (4,818 ) Books of business and other intangibles, net 14,776 15,532 Total other intangible assets, net $ 121,673 $ 127,340
Estimated Remaining Amortization Expense	The Company’s estimated remaining amortization expense on other intangible assets as of March 31, 2020 is as follows: (In thousands) Year Amortization Expense Remainder of 2020 $ 10,120 2021 13,436 2022 13,384 2023 13,101 2024 12,199 Thereafter 59,433 Total $ 121,673

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Provision for Income Taxes	The provision for income taxes is comprised of the following components for the periods indicated below: Three Months Ended (In thousands) 2020 2019 Income taxes currently payable $ 22,280 $ 10,317 Deferred income taxes (1,586 ) 2,081 Provision for income taxes $ 20,694 $ 12,398
Schedule of Deferred Tax Assets and Liabilities	The tax effects of temporary differences between the tax basis of assets and liabilities and their financial reporting amounts that give rise to deferred income tax assets and liabilities, and their approximate tax effects, are as follows: (In thousands) March 31, 2020 December 31, 2019 Deferred tax assets: Loans acquired $ 16,606 $ 20,783 Allowance for credit losses 60,678 16,732 Valuation of foreclosed assets 2,636 2,626 Tax NOLs from acquisition 17,467 18,118 Deferred compensation payable 2,866 2,750 Accrued equity and other compensation 5,914 6,677 Acquired securities — 3,393 Right-of-use lease liability 9,646 10,221 Allowance for unfunded commitments 7,376 — Other 5,414 7,886 Gross deferred tax assets 128,603 89,186 Deferred tax liabilities: Goodwill and other intangible amortization (40,378 ) (41,221 ) Accumulated depreciation (36,731 ) (36,554 ) Right-of-use lease asset (9,620 ) (10,176 ) Unrealized gain on available-for-sale securities (11,725 ) (3,720 ) Deferred loan fees and costs (2,994 ) (3,018 ) Acquired securities (771 ) — Other (5,332 ) (4,633 ) Gross deferred tax liabilities (107,551 ) (99,322 ) Net deferred tax asset (liability) $ 21,052 $ (10,136 )
Reconciliation of Income Tax Expense	A reconciliation of income tax expense at the statutory rate to the Company’s actual income tax expense is shown for the periods indicated below: Three Months Ended (In thousands) 2020 2019 Computed at the statutory rate (21%) $ 20,560 $ 12,620 Increase (decrease) in taxes resulting from: State income taxes, net of federal tax benefit 2,063 1,345 Discrete items related to ASU 2016-09 26 (26 ) Tax exempt interest income (1,421 ) (961 ) Tax exempt earnings on BOLI (319 ) (179 ) Federal tax credits (1,034 ) (729 ) Other differences, net 819 328 Actual tax provision $ 20,694 $ 12,398

Securities Sold Under Agreeme_2

Securities Sold Under Agreements to Repurchase (Tables)	3 Months Ended
	Mar. 31, 2020
Banking and Thrift [Abstract]
Contractual Maturity of Securities Sold Under Agreements to Repurchase	The remaining contractual maturity of the securities sold under agreements to repurchase in the consolidated balance sheets as of March 31, 2020 and December 31, 2019 is presented in the following tables. Remaining Contractual Maturity of the Agreements (In thousands) Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total March 31, 2020 Repurchase agreements: U.S. Government agencies $ 334,064 $ — $ — $ — $ 334,064 December 31, 2019 Repurchase agreements: U.S. Government agencies $ 133,220 $ — $ — $ — $ 133,220

Other Borrowings and Subordin_2

Other Borrowings and Subordinated Notes and Debentures (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt	Debt at March 31, 2020 and December 31, 2019 consisted of the following components: (In thousands) March 31, 2020 December 31, 2019 Other Borrowings FHLB advances, net of discount, due 2020 to 2034, 0.23% to 7.37% secured by real estate loans $ 1,362,295 $ 1,262,691 Other long-term debt 34,534 34,908 Total other borrowings 1,396,829 1,297,599 Subordinated Notes and Debentures Subordinated notes payable, due 4/1/2028, fixed-to-floating rate (fixed rate of 5.00% through 3/31/2023, floating rate of 2.15% above the three month LIBOR rate, reset quarterly) 330,000 330,000 Trust preferred securities, net of discount, due 9/15/2037, floating rate of 1.37% above the three month LIBOR rate, reset quarterly 10,310 10,310 Trust preferred securities, net of discount, due 6/6/2037, floating rate of 1.57% above the three month LIBOR rate, reset quarterly, callable without penalty 10,310 10,310 Trust preferred securities, due 12/15/2035, floating rate of 1.45% above the three month LIBOR rate, reset quarterly, callable without penalty 6,702 6,702 Trust preferred securities, net of discount, due 6/15/2037, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty 25,054 25,015 Trust preferred securities, net of discount, due 12/15/2036, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty 3,009 3,004 Other subordinated debentures, due 12/31/2036, floating rate of prime rate minus 1.1%, reset quarterly 5,927 5,927 Unamortized debt issuance costs (2,916 ) (3,008 ) Total subordinated notes and debentures 388,396 388,260 Total other borrowings and subordinated debt $ 1,785,225 $ 1,685,859
Aggregate Annual Maturities of Long-term Debt	Aggregate annual maturities of long-term debt at March 31, 2020 , are as follows: Year (In thousands) Remainder of 2020 $ 2,946 2021 3,016 2022 2,187 2023 2,366 2024 2,446 Thereafter 422,264 Total $ 435,225

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Compensation Plans	The table below summarizes the transactions under the Company’s active stock-based compensation plans for the three months ended March 31, 2020 : Stock Options Outstanding Non-vested Stock Awards Outstanding Non-vested Stock Units Outstanding (Shares in thousands) Number of Shares Weighted Average Exercise Price Number of Shares Weighted Average Grant-Date Fair Value Number of Shares Weighted Average Grant-Date Fair Value Balance, January 1, 2020 692 $ 22.46 21 $ 23.19 1,152 $ 26.79 Granted — — — — 425 23.26 Stock options exercised (1 ) 10.71 — — — — Stock awards/units vested (earned) — — (4 ) 20.88 (351 ) 26.35 Forfeited/expired — — — — (42 ) 27.01 Balance, March 31, 2020 691 $ 22.48 17 $ 23.75 1,184 $ 25.64 Exercisable, March 31, 2020 691 $ 22.48
Stock Options	The following table summarizes information about stock options under the plans outstanding at March 31, 2020 : Options Outstanding Options Exercisable Range of Exercise Prices Number of Shares (In thousands) Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price Number of Shares (In thousands) Weighted Average Exercise Price $ 9.46 — $ 9.46 1 1.80 $9.46 1 $9.46 10.65 — 10.65 3 2.83 10.65 3 10.65 20.29 — 20.29 71 3.68 20.29 71 20.29 20.36 — 20.36 2 4.63 20.36 2 20.36 22.20 — 22.20 74 3.88 22.20 74 22.20 22.75 — 22.75 436 4.39 22.75 436 22.75 23.51 — 23.51 97 4.82 23.51 97 23.51 24.07 — 24.07 7 5.46 24.07 7 24.07 $ 9.46 — $ 24.07 691 4.32 $22.48 691 $22.48
Restricted Performance Stock Unit Activity	The table below summarizes the Company’s performance stock unit activity for the three months ended March 31, 2020 : (In thousands) Performance Stock Units Non-vested, January 1, 2020 199 Granted 116 Vested (earned) (80 ) Forfeited (11 ) Non-vested, March 31, 2020 224

Earnings Per Share ("EPS") (Tab

Earnings Per Share ("EPS") (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Computation of Earnings Per Share	The computation of earnings per share is as follows: Three Months Ended (In thousands, except per share data) 2020 2019 Net income available to common stockholders $ 77,223 $ 47,695 Average common shares outstanding 112,888 92,520 Average potential dilutive common shares 249 351 Average diluted common shares 113,137 92,871 Basic earnings per share $ 0.68 $ 0.52 Diluted earnings per share $ 0.68 $ 0.51

Additional Cash Flow Informat_2

Additional Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Additional Cash Flow Information	The following is a summary of the Company’s additional cash flow information: Three Months Ended (In thousands) 2020 2019 Interest paid $ 39,388 $ 38,047 Income taxes paid (refunded) 92 (54 ) Transfers of loans to foreclosed assets held for sale 508 569 Transfers of premises to foreclosed assets and other real estate owned 3,120 — Right-of-use lease assets obtained in exchange for lessee operating lease liabilities (adoption of ASU 2016-02) — 32,757 Transfers of loans to other assets held for sale 114,925 — Transfers of deposits to other liabilities held for sale 58,405 —

Other Income and Other Operat_2

Other Income and Other Operating Expenses (Tables)	3 Months Ended
	Mar. 31, 2020
Other Income and Expenses [Abstract]
Other Operating Expenses	Other operating expenses consisted of the following: Three Months Ended (In thousands) 2020 2019 Professional services $ 5,829 $ 4,323 Postage 2,236 1,726 Telephone 2,185 1,619 Credit card expense 4,382 3,860 Marketing 4,385 3,057 Software and technology 6,415 4,496 Operating supplies 936 618 Amortization of intangibles 3,413 2,641 Branch right sizing expense 238 45 Other expense 8,769 7,677 Total other operating expenses $ 38,788 $ 30,062

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Financial Instruments Measured on Recurring Basis	The following table sets forth the Company’s financial assets by level within the fair value hierarchy that were measured at fair value on a recurring basis as of March 31, 2020 and December 31, 2019 . Fair Value Measurements Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) March 31, 2020 Available-for-sale securities U.S. Treasury $ 424,989 $ 424,989 $ — $ — U.S. Government agencies 161,289 — 161,289 — Mortgage-backed securities 1,179,837 — 1,179,837 — State and political subdivisions 678,243 — 678,243 — Other securities 22,282 — 22,282 — Other assets held for sale 115,315 — — 115,315 Derivative asset 42,102 — 42,102 — Other liabilities held for sale (58,405 ) — — (58,405 ) Derivative liability (42,482 ) — (42,482 ) — December 31, 2019 Available-for-sale securities U.S. Treasury $ 449,729 $ 449,729 $ — $ — U.S. Government agencies 194,249 — 194,249 — Mortgage-backed securities 1,742,945 — 1,742,945 — States and political subdivisions 880,524 — 880,524 — Other securities 20,896 — 20,896 — Other assets held for sale 260,332 — — 260,332 Derivative asset 14,903 — 14,903 — Other liabilities held for sale (159,853 ) — — (159,853 ) Derivative liability (12,650 ) — (12,650 ) —
Financial Assets Measure on Nonrecurring Basis	The following table sets forth the Company’s financial assets by level within the fair value hierarchy that were measured at fair value on a nonrecurring basis as of March 31, 2020 and December 31, 2019 . Fair Value Measurements Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) March 31, 2020 Individually assessed loans (1) (2) (collateral-dependent) $ 38,901 $ — $ — $ 38,901 Foreclosed assets and other real estate owned (1) 2,050 — — 2,050 December 31, 2019 Individually assessed loans (1) (2) (collateral-dependent) $ 49,190 $ — $ — $ 49,190 Foreclosed assets and other real estate owned (1) 18,798 — — 18,798 ________________________ (1) These amounts represent the resulting carrying amounts on the consolidated balance sheets for collateral-dependent loans and foreclosed assets and other real estate owned for which fair value re-measurements took place during the period. (2) Identified reserves of $27,131,000 and $1,297,000 were related to collateral-dependent loans for which fair value re-measurements took place during the periods ended March 31, 2020 and December 31, 2019 , respectively.
Estimated Fair Values and Related Carrying Amounts	The estimated fair values, and related carrying amounts, of the Company’s financial instruments are as follows: Carrying Fair Value Measurements (In thousands) Amount Level 1 Level 2 Level 3 Total March 31, 2020 Financial assets: Cash and cash equivalents $ 1,737,199 $ 1,737,199 $ — $ — $ 1,737,199 Interest bearing balances due from banks - time 4,309 — 4,309 — 4,309 Held-to-maturity securities 53,968 — 55,714 — 55,714 Mortgage loans held for sale 49,984 — — 49,984 49,984 Interest receivable 57,039 — 57,039 — 57,039 Loans, net 14,131,082 — — 14,160,286 14,160,286 Financial liabilities: Non-interest bearing transaction accounts 3,572,244 — 3,572,244 — 3,572,244 Interest bearing transaction accounts and savings deposits 8,840,678 — 8,840,678 — 8,840,678 Time deposits 3,146,811 — — 3,163,694 3,163,694 Federal funds purchased and securities sold under agreements to repurchase 377,859 — 377,859 — 377,859 Other borrowings 1,396,829 — 1,411,137 — 1,411,137 Subordinated notes and debentures 388,396 — 407,301 — 407,301 Interest payable 15,258 — 15,258 — 15,258 December 31, 2019 Financial assets: Cash and cash equivalents $ 996,623 $ 996,623 $ — $ — $ 996,623 Interest bearing balances due from banks - time 4,554 — 4,554 — 4,554 Held-to-maturity securities 40,927 — 41,855 — 41,855 Mortgage loans held for sale 58,102 — — 58,102 58,102 Interest receivable 62,707 — 62,707 — 62,707 Loans, net 14,357,460 — — 14,290,188 14,290,188 Financial liabilities: Non-interest bearing transaction accounts 3,741,093 — 3,741,093 — 3,741,093 Interest bearing transaction accounts and savings deposits 9,090,878 — 9,090,878 — 9,090,878 Time deposits 3,276,969 — — 3,270,333 3,270,333 Federal funds purchased and securities sold under agreements to repurchase 150,145 — 150,145 — 150,145 Other borrowings 1,297,599 — 1,298,011 — 1,298,011 Subordinated debentures 388,260 — 397,088 — 397,088 Interest payable 12,898 — 12,898 — 12,898

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table summarizes the fair values of loan derivative contracts recorded in the accompanying consolidated balance sheets. March 31, 2020 December 31, 2019 (In thousands) Notional Fair Value Notional Fair Value Derivative assets $ 440,119 $ 42,102 $ 401,969 $ 14,903 Derivative liabilities 449,613 42,482 387,075 12,650

Preparation of Interim Financ_3

Preparation of Interim Financial Statements (Details) $ in Thousands	Jan. 01, 2020USD ($)	Mar. 31, 2020USD ($)financial_center	Dec. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Number of financial centers | financial_center		240
Allowance for credit loss		$ 243,195
Unfunded commitments, allowance for credit loss		29,400	$ 8,400
Cumulative effect on retained earnings		$ 778,893	$ 848,848
Impact of adoption of 2016-13 | Accounting Standards Update 2016-13
Lessee, Lease, Description [Line Items]
Allowance for credit loss	$ 151,400
Unfunded commitments, allowance for credit loss	24,000
Debt securities, allowance for credit loss	742
Cumulative effect on retained earnings	128,100
Purchased with credit deterioration, allowance for credit loss	$ 5,400

Acquisitions - Textual (Details

Acquisitions - Textual (Details) $ / shares in Units, $ in Thousands	Oct. 31, 2019USD ($)$ / sharesshares	Apr. 12, 2019USD ($)shares	Mar. 31, 2020USD ($)financial_center$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Oct. 30, 2019USD ($)financial_center	Oct. 29, 2019$ / sharesshares	Apr. 11, 2019USD ($)financial_center	Feb. 27, 2009$ / sharesshares
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01	$ 0.01				$ 0.01
Number of financial centers | financial_center			240
Goodwill			$ 1,064,978	$ 1,055,520
Preferred stock, shares authorized (in shares) | shares			40,040,000	40,040,000				40,040,000
Preferred stock, shares issued (in shares) | shares			767	767
Preferred stock, shares outstanding (in shares) | shares			767	767
Landrum Company
Business Acquisition [Line Items]
Shares issued (in shares) | shares	17,349,722
Number of financial centers | financial_center					39
Assets acquired	$ 3,399,127				$ 3,381,889
Loans acquired	2,005,486				2,049,137
Deposits acquired	3,049,600				3,049,301
Goodwill	$ 140,797			$ 131,300	$ 407
Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Shares issued (in shares) | shares		3,999,623
Number of financial centers | financial_center							22
Assets acquired		$ 1,534,312					$ 1,549,954
Loans acquired		1,096,870					1,138,527
Deposits acquired		1,225,267					$ 1,227,058
Goodwill		78,493		$ 78,500
Payments to acquire businesses, gross		62,700
Stock issued for Reliance acquisition		$ 42,000
Common Class A | Landrum Company
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01
Preferred Class B | Landrum Company
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01
Series E Preferred Stock | Landrum Company
Business Acquisition [Line Items]
Shares issued, conversion ratio (in shares)	17,350,000
Series D Preferred Stock | Landrum Company
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01
Shares issued, conversion ratio (in shares)	1
Series D Preferred Stock | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares						$ 0.01
Preferred Stock | Landrum Company
Business Acquisition [Line Items]
Shares issued (in shares) | shares	767
Series A or B Preferred Stock | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Shares issued, conversion ratio (in shares)		1
Series C Preferred Stock | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Shares issued, conversion ratio (in shares)		1
Preferred stock, shares authorized (in shares) | shares						140
Preferred stock, shares issued (in shares) | shares						0
Preferred stock, shares outstanding (in shares) | shares						0

Acquisitions - Assets Acquired

Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Apr. 12, 2019	Mar. 31, 2020	Dec. 31, 2019	Oct. 30, 2019	Apr. 11, 2019
Liabilities Assumed
Goodwill			$ 1,064,978	$ 1,055,520
Landrum Company
Assets Acquired
Cash and due from banks	$ 215,285				$ 215,285
Due from banks - time	248				248
Investment securities	1,025,983				1,021,755
Loans acquired	2,005,486				2,049,137
Allowance for loan losses					(22,736)
Foreclosed assets	190				373
Premises and equipment	82,745				63,878
Bank owned life insurance	19,206				19,206
Other assets	20,523				33,924
Total assets acquired	3,399,127				3,381,889
Liabilities Assumed
Non-interest bearing transaction accounts	716,675				716,675
Interest bearing transaction accounts and savings deposits	1,465,429				1,465,429
Time deposits	867,496				867,197
Total deposits	3,049,600				3,049,301
Other borrowings	10,055				10,055
Subordinated debentures	33,917				34,794
Accrued interest and other liabilities	30,573				31,057
Total liabilities assumed	3,124,145				3,125,207
Total equity assumed					256,682
Total liabilities and equity assumed	3,124,145				3,381,889
Net assets acquired	274,982
Purchase price	415,779
Goodwill	140,797			131,300	407
Landrum Company | Fair Value Adjustments
Assets Acquired
Cash and due from banks	0
Due from banks - time	0
Investment securities	4,228
Loans acquired	(43,651)
Allowance for loan losses	22,736
Foreclosed assets	(183)
Premises and equipment	18,867
Bank owned life insurance	0
Other assets	(13,401)
Total assets acquired	17,238
Liabilities Assumed
Non-interest bearing transaction accounts	0
Interest bearing transaction accounts and savings deposits	0
Time deposits	299
Total deposits	299
Other borrowings	0
Subordinated debentures	(877)
Accrued interest and other liabilities	(484)
Total liabilities assumed	(1,062)
Total equity assumed	(256,682)
Total liabilities and equity assumed	(257,744)
Goodwill	(407)
Reliance Bancshares, Inc.
Assets Acquired
Cash and due from banks		$ 25,693				$ 25,693
Due from banks - time		502				502
Investment securities		286,110				287,983
Loans acquired		1,096,870				1,138,527
Allowance for loan losses		0				(10,808)
Foreclosed assets		5,912				11,092
Premises and equipment		29,451				32,452
Bank owned life insurance		39,348				39,348
Core deposit intangible		18,350				0
Other assets		32,076				25,165
Total assets acquired		1,534,312				1,549,954
Liabilities Assumed
Non-interest bearing transaction accounts		108,812				108,845
Interest bearing transaction accounts and savings deposits		639,798				639,798
Time deposits		476,657				478,415
Total deposits		1,225,267				1,227,058
Securities sold under agreement to repurchase		14,146				14,146
Other borrowings		157,400				162,900
Accrued interest and other liabilities		8,453				8,185
Total liabilities assumed		1,405,266				1,412,289
Total equity assumed		0				137,665
Total liabilities and equity assumed		1,405,266				$ 1,549,954
Net assets acquired		129,046
Purchase price		207,539
Goodwill		78,493		$ 78,500
Reliance Bancshares, Inc. | Fair Value Adjustments
Assets Acquired
Cash and due from banks		0
Due from banks - time		0
Investment securities		(1,873)
Loans acquired		(41,657)
Allowance for loan losses		10,808
Foreclosed assets		(5,180)
Premises and equipment		(3,001)
Bank owned life insurance		0
Core deposit intangible		18,350
Other assets		6,911
Total assets acquired		(15,642)
Liabilities Assumed
Non-interest bearing transaction accounts		(33)
Interest bearing transaction accounts and savings deposits		0
Time deposits		(1,758)
Total deposits		(1,791)
Securities sold under agreement to repurchase		0
Other borrowings		(5,500)
Accrued interest and other liabilities		268
Total liabilities assumed		(7,023)
Total equity assumed		(137,665)
Total liabilities and equity assumed		$ (144,688)
Core deposit intangible | Landrum Company
Assets Acquired
Core deposit intangible	24,345				0
Core deposit intangible | Landrum Company | Fair Value Adjustments
Assets Acquired
Core deposit intangible	24,345
Other intangibles | Landrum Company
Assets Acquired
Core deposit intangible	5,116				$ 412
Other intangibles | Landrum Company | Fair Value Adjustments
Assets Acquired
Core deposit intangible	$ 4,704

Investment Securities - Summary

Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Held-to-Maturity
Amortized Cost	$ 54,377	$ 40,927
Allowance for credit losses on HTM	(409)	0
Net Carrying Amount	53,968	40,927
Gross Unrealized Gains	1,759	987
Gross Unrealized (Losses)	(13)	(59)
Estimated Fair Value	55,714	41,855
Available-for-sale
Amortized Cost	2,418,498	3,263,151
Allowance for credit losses on AFS	(269)	0
Gross Unrealized Gains	53,884	31,740
Gross Unrealized (Losses)	(5,473)	(6,548)
Estimated Fair Value	2,466,640	3,288,343
U.S. Treasury
Available-for-sale
Amortized Cost	425,032	449,729
Allowance for credit losses on AFS	0	0
Gross Unrealized Gains	0	112
Gross Unrealized (Losses)	(43)	(112)
Estimated Fair Value	424,989	449,729
U.S. Government agencies
Available-for-sale
Amortized Cost	161,473	194,207
Allowance for credit losses on AFS	0	0
Gross Unrealized Gains	707	1,313
Gross Unrealized (Losses)	(891)	(1,271)
Estimated Fair Value	161,289	194,249
Mortgage-backed securities
Held-to-Maturity
Amortized Cost	27,121	10,796
Allowance for credit losses on HTM	0	0
Net Carrying Amount	27,121	10,796
Gross Unrealized Gains	668	71
Gross Unrealized (Losses)	(1)	(59)
Estimated Fair Value	27,788	10,808
Available-for-sale
Amortized Cost	1,150,878	1,738,584
Allowance for credit losses on AFS	0	0
Gross Unrealized Gains	32,068	8,510
Gross Unrealized (Losses)	(3,109)	(4,149)
Estimated Fair Value	1,179,837	1,742,945
State and political subdivisions
Held-to-Maturity
Amortized Cost	26,082	27,082
Allowance for credit losses on HTM	(97)	0
Net Carrying Amount	25,985	27,082
Gross Unrealized Gains	981	849
Gross Unrealized (Losses)	(12)	0
Estimated Fair Value	26,954	27,931
Available-for-sale
Amortized Cost	659,350	860,539
Allowance for credit losses on AFS	(95)	0
Gross Unrealized Gains	20,243	20,983
Gross Unrealized (Losses)	(1,255)	(998)
Estimated Fair Value	678,243	880,524
Other securities
Held-to-Maturity
Amortized Cost	1,174	3,049
Allowance for credit losses on HTM	(312)	0
Net Carrying Amount	862	3,049
Gross Unrealized Gains	110	67
Gross Unrealized (Losses)	0	0
Estimated Fair Value	972	3,116
Available-for-sale
Amortized Cost	21,765	20,092
Allowance for credit losses on AFS	(174)	0
Gross Unrealized Gains	866	822
Gross Unrealized (Losses)	(175)	(18)
Estimated Fair Value	$ 22,282	$ 20,896

Investment Securities - Securit

Investment Securities - Securities With Unrealized Losses (Details) $ in Thousands	Mar. 31, 2020USD ($)
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	$ 507,520
Available-for-sale, less than 12 months, gross unrealized losses	(2,518)
Available-for-sale, 12 months or more, estimated fair value	133,004
Available-for-sale, 12 months or more, gross unrealized losses	(2,686)
Available-for-sale, total, estimated fair value	640,524
Available-for-sale, total, gross unrealized losses	(5,204)
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	424,989
Available-for-sale, less than 12 months, gross unrealized losses	(43)
Available-for-sale, 12 months or more, estimated fair value	0
Available-for-sale, 12 months or more, gross unrealized losses	0
Available-for-sale, total, estimated fair value	424,989
Available-for-sale, total, gross unrealized losses	(43)
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	0
Available-for-sale, less than 12 months, gross unrealized losses	0
Available-for-sale, 12 months or more, estimated fair value	58,056
Available-for-sale, 12 months or more, gross unrealized losses	(891)
Available-for-sale, total, estimated fair value	58,056
Available-for-sale, total, gross unrealized losses	(891)
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	57,718
Available-for-sale, less than 12 months, gross unrealized losses	(1,318)
Available-for-sale, 12 months or more, estimated fair value	74,523
Available-for-sale, 12 months or more, gross unrealized losses	(1,791)
Available-for-sale, total, estimated fair value	132,241
Available-for-sale, total, gross unrealized losses	(3,109)
State and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	24,813
Available-for-sale, less than 12 months, gross unrealized losses	(1,157)
Available-for-sale, 12 months or more, estimated fair value	425
Available-for-sale, 12 months or more, gross unrealized losses	(4)
Available-for-sale, total, estimated fair value	25,238
Available-for-sale, total, gross unrealized losses	$ (1,161)

Investment Securities - Textual

Investment Securities - Textual (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, interest receivable	$ 334,000
Available-for-sale, interest receivable	9,700,000
Available-for-sale securities	2,466,640,000		$ 3,288,343,000
Securities valued at less than historical cost, amount	$ 640,524,000
Securities valued at less than historical cost (as percent)	26.00%
Decrease in available-for-sale provision for credit losses	$ (104,000,000)
Securities pledged as collateral	1,740,000,000	$ 2,700,000	$ 1,730,000,000
Realized gains	32,100,000
Realized losses	(2,080)	$ 0
Investments sold, amount	$ 1,100,000,000
Income tax benefit related to security gains (losses) (as percent)			26.135%

Investment Securities - Allowan

Investment Securities - Allowance for Credit Losses HTM (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	$ 0
Provision for credit loss expense	40
Balance, March 31, 2020	409
State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	0
Provision for credit loss expense	39
Balance, March 31, 2020	97
Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	0
Provision for credit loss expense	1
Balance, March 31, 2020	312
Impact of adoption of 2016-13
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	369
Impact of adoption of 2016-13 | State and political subdivisions
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	58
Impact of adoption of 2016-13 | Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Balance, January 1, 2020	$ 311

Investment Securities - Allow_2

Investment Securities - Allowance for Credit Losses AFS (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Balance, January 1, 2020	$ 0
Credit losses on securities not previously recorded	218
Net increase (decrease) in allowance on previously impaired securities	(322)
Balance, March 31, 2020	269
Impact of adoption of 2016-13
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Balance, January 1, 2020	373
State and political subdivisions
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Balance, January 1, 2020	0
Credit losses on securities not previously recorded	44
Net increase (decrease) in allowance on previously impaired securities	(322)
Balance, March 31, 2020	95
State and political subdivisions | Impact of adoption of 2016-13
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Balance, January 1, 2020	373
Other securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Balance, January 1, 2020	0
Credit losses on securities not previously recorded	174
Net increase (decrease) in allowance on previously impaired securities	0
Balance, March 31, 2020	174
Other securities | Impact of adoption of 2016-13
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Balance, January 1, 2020	$ 0

Investment Securities - Credit

Investment Securities - Credit Quality Indicator (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	$ 54,377	$ 40,927
State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	26,082	27,082
Other securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	1,174	$ 3,049
Aaa/AAA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	2,111
Aaa/AAA | Other securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	0
Aa/AA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	19,084
Aa/AA | Other securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	0
A | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	1,695
A | Other securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	0
Not Rated | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	3,192
Not Rated | Other securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	1,174
Not Guaranteed or Pre-Refunded | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	17,796
Not Guaranteed or Pre-Refunded | Aaa/AAA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	2,111
Not Guaranteed or Pre-Refunded | Aa/AA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	12,596
Not Guaranteed or Pre-Refunded | A | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	766
Not Guaranteed or Pre-Refunded | Not Rated | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	2,323
Other Credit Enhancement or Insurance | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	7,502
Other Credit Enhancement or Insurance | Aaa/AAA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	0
Other Credit Enhancement or Insurance | Aa/AA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	6,203
Other Credit Enhancement or Insurance | A | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	929
Other Credit Enhancement or Insurance | Not Rated | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	370
Pre-Refunded | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	784
Pre-Refunded | Aaa/AAA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	0
Pre-Refunded | Aa/AA | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	285
Pre-Refunded | A | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	0
Pre-Refunded | Not Rated | State and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Net carrying amount	$ 499

Investment Securities - Income

Investment Securities - Income Earned on Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Non-taxable:
Total	$ 18,943	$ 16,281
Held-to-maturity
Taxable:
Taxable	171	438
Non-taxable:
Non-taxable	72	1,162
Available-for-sale
Taxable:
Taxable	12,581	11,520
Non-taxable:
Non-taxable	$ 6,119	$ 3,161

Investment Securities - Maturit

Investment Securities - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, amortized cost, one year or less	$ 4,543
Held-to-maturity, amortized cost, after one through five years	15,414
Held-to-maturity, amortized cost, after five through ten years	7,299
Held-to-maturity, amortized cost, after ten years	0
Held-to-maturity, amortized cost, securities not due on a single maturity date	27,121
Amortized Cost	54,377	$ 40,927
Held-to-maturity, fair value, one year or less	4,563
Held-to-maturity, fair value, after one through five years	15,769
Held-to-maturity, fair value, after five through ten years	7,594
Held-to-maturity, fair value, after ten years	0
Held-to-maturity, fair value, securities not due on a single maturity date	27,788
Held-to-maturity, fair value, total	55,714	41,855
Available-for-sale, amortized cost, one year or less	437,199
Available-for-sale, amortized cost, after one through five years	34,541
Available-for-sale, amortized cost, after five through ten years	108,605
Available-for-sale, amortized cost, after ten years	686,714
Available-for-sale, amortized cost, securities not due on a single maturity date	1,150,878
Available-for-sale, amortized cost, other securities (no maturity)	561
Amortized Cost	2,418,498	3,263,151
Available-for-sale, fair value, one year or less	437,187
Available-for-sale, fair value, after one through five years	34,889
Available-for-sale, fair value, after five through ten years	109,611
Available-for-sale, fair value, after ten years	703,839
Available-for-sale, fair value, securities not due on a single maturity date	1,179,837
Available-for-sale, fair value, other securities (no maturity)	1,277
Available-for-sale, fair value, total	$ 2,466,640	$ 3,288,343

Other Assets and Other Liabil_2

Other Assets and Other Liabilities Held for Sale (Details) - USD ($) $ in Millions	Aug. 01, 2020	May 31, 2020	Feb. 28, 2020	Jul. 31, 2020	Mar. 31, 2020
Business Acquisition [Line Items]
Gain on sale of business					$ 5.9
First Western Trust Bank
Business Acquisition [Line Items]
Total loans, excluding loans not subject to branch purchase					114.9
Total deposits, excluding deposits not subject to branch purchase					$ 58.4
Forecast | First Western Trust Bank
Business Acquisition [Line Items]
Post closing adjustment multiplier, percent	8.06%	6.06%		7.06%
Disposal Group, Held-for-sale, Not Discontinued Operations | Spirit of Texas Bank, SSB
Business Acquisition [Line Items]
Gain on sale of business			$ 5.9

Loans and Allowance for Loan _3

Loans and Allowance for Loan Losses - Textual (Details)	3 Months Ended
	Mar. 31, 2020USD ($)loan	Mar. 31, 2019USD ($)loan	Dec. 31, 2019USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 14,374,277,000		$ 14,425,704,000
Premiums and discounts associated with acquired loans	72,400,000	$ 91,600,000
Financing receivable, accrued interest excluded from amortized costs	47,000,000		48,900,000
Nonaccrual loans with no allowance for credit loss	$ 22,400,000
Troubled debt, number of contracts	0	0
Foreclosed assets and other real estate owned	$ 20,805,000		19,121,000
Financing receivable, collateral dependent, amount	75,670,000
Unfunded commitments, allowance for credit loss	29,400,000		8,400,000
(Benefit) provision for credit losses on unfunded commitments	(3,000,000)	$ 300,000
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in process of foreclosure, amount	5,301,000		5,789,000
Energy
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, collateral dependent, amount	43,573,000
Increase in specific provisions	22,000,000
OREO Received in Full or Partial Satisfaction of Loans | Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed assets and other real estate owned	2,672,000		4,458,000
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	10,833,765,000		$ 11,021,940,000
Real Estate | OREO Received in Full or Partial Satisfaction of Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance prior to TDR	$ 0
Commercial Real Estate | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans with subsequent default | loan	0	1
Write-down of impaired loans		$ 138,000

Loans and Allowance for Loan _4

Loans and Allowance for Loan Losses - Loan Portfolio by Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Loans	$ 14,374,277	$ 14,425,704
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans	456,466	453,997
Consumer | Credit cards
Loans and Leases Receivable Disclosure [Line Items]
Loans	188,596	204,802
Consumer | Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans	267,870	249,195
Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Loans	10,833,765	11,021,940
Real Estate | Construction and development
Loans and Leases Receivable Disclosure [Line Items]
Loans	2,024,118	2,248,673
Real Estate | Single family residential
Loans and Leases Receivable Disclosure [Line Items]
Loans	2,343,543	2,414,753
Real Estate | Other commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	6,466,104	6,358,514
Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	2,506,007	2,642,644
Commercial | Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	2,314,472	2,451,119
Commercial | Agricultural
Loans and Leases Receivable Disclosure [Line Items]
Loans	191,535	191,525
Other
Loans and Leases Receivable Disclosure [Line Items]
Loans	$ 578,039	$ 307,123

Loans and Allowance for Loan _5

Loans and Allowance for Loan Losses - Nonaccrual Loans, Excluding Loans Acquired, Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	$ 155,863	$ 93,330
Consumer
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	2,376	2,087
Consumer | Credit cards
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	265	382
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	2,111	1,705
Real Estate
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	73,861	49,566
Real Estate | Construction and development
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	6,604	5,289
Real Estate | Single family residential
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	30,829	27,695
Real Estate | Other commercial
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	36,428	16,582
Commercial
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	79,626	41,677
Commercial | Commercial
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	78,944	40,924
Commercial | Agricultural
Financing Receivable, Past Due [Line Items]
Loans in nonaccrual status	$ 682	$ 753

Loans and Allowance for Loan _6

Loans and Allowance for Loan Losses - Age Analysis of Past Due Loans, Excluding Loans Acquired, Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 137,695	$ 93,989
Current	14,236,582	14,331,715
Total Loans	14,374,277	14,425,704
90 Days Past Due & Accruing	1,160	856
Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	79,617	57,289
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	58,078	36,700
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	6,862	7,108
Current	449,604	446,889
Total Loans	456,466	453,997
90 Days Past Due & Accruing	115	259
Consumer | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,406	5,732
Consumer | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,456	1,376
Consumer | Credit cards
Financing Receivable, Past Due [Line Items]
Total Past Due	1,191	1,489
Current	187,405	203,313
Total Loans	188,596	204,802
90 Days Past Due & Accruing	115	259
Consumer | Credit cards | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	866	848
Consumer | Credit cards | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	325	641
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	5,671	5,619
Current	262,199	243,576
Total Loans	267,870	249,195
90 Days Past Due & Accruing	0	0
Consumer | Other consumer | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4,540	4,884
Consumer | Other consumer | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,131	735
Real Estate
Financing Receivable, Past Due [Line Items]
Total Past Due	88,405	61,072
Current	10,745,360	10,960,868
Total Loans	10,833,765	11,021,940
90 Days Past Due & Accruing	322	597
Real Estate | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	57,473	39,755
Real Estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	30,932	21,317
Real Estate | Construction and development
Financing Receivable, Past Due [Line Items]
Total Past Due	7,726	6,870
Current	2,016,392	2,241,803
Total Loans	2,024,118	2,248,673
90 Days Past Due & Accruing	0	0
Real Estate | Construction and development | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,713	5,792
Real Estate | Construction and development | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,013	1,078
Real Estate | Single family residential
Financing Receivable, Past Due [Line Items]
Total Past Due	46,482	40,107
Current	2,297,061	2,374,646
Total Loans	2,343,543	2,414,753
90 Days Past Due & Accruing	321	597
Real Estate | Single family residential | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	31,236	26,318
Real Estate | Single family residential | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	15,246	13,789
Real Estate | Other commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	34,197	14,095
Current	6,431,907	6,344,419
Total Loans	6,466,104	6,358,514
90 Days Past Due & Accruing	1	0
Real Estate | Other commercial | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	23,524	7,645
Real Estate | Other commercial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	10,673	6,450
Commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	42,428	25,809
Current	2,463,579	2,616,835
Total Loans	2,506,007	2,642,644
90 Days Past Due & Accruing	723	0
Commercial | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	16,738	11,802
Commercial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	25,690	14,007
Commercial | Commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	41,491	24,130
Current	2,272,981	2,426,989
Total Loans	2,314,472	2,451,119
90 Days Past Due & Accruing	723	0
Commercial | Commercial | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	16,361	10,579
Commercial | Commercial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	25,130	13,551
Commercial | Agricultural
Financing Receivable, Past Due [Line Items]
Total Past Due	937	1,679
Current	190,598	189,846
Total Loans	191,535	191,525
90 Days Past Due & Accruing	0	0
Commercial | Agricultural | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	377	1,223
Commercial | Agricultural | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	560	456
Other
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Current	578,039	307,123
Total Loans	578,039	307,123
90 Days Past Due & Accruing	0	$ 0
Other | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0
Other | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 0

Loans and Allowance for Loan _7

Loans and Allowance for Loan Losses - Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired, Segregated by Class of Loans (Details) - Loans, Excluding Acquired Loans - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		$ 90,639
Recorded Investment With No Allowance		33,043
Recorded Investment With Allowance		35,889
Total Recorded Investment		68,932
Related Allowance		5,747
Average Investment in Impaired Loans	$ 48,675
Interest Income Recognized	375
Consumer
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		1,919
Recorded Investment With No Allowance		1,760
Recorded Investment With Allowance		0
Total Recorded Investment		1,760
Related Allowance		0
Average Investment in Impaired Loans	2,174
Interest Income Recognized	43
Consumer | Credit cards
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		382
Recorded Investment With No Allowance		382
Recorded Investment With Allowance		0
Total Recorded Investment		382
Related Allowance		0
Average Investment in Impaired Loans	317
Interest Income Recognized	30
Consumer | Other consumer
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		1,537
Recorded Investment With No Allowance		1,378
Recorded Investment With Allowance		0
Total Recorded Investment		1,378
Related Allowance		0
Average Investment in Impaired Loans	1,857
Interest Income Recognized	13
Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		34,759
Recorded Investment With No Allowance		24,318
Recorded Investment With Allowance		6,775
Total Recorded Investment		31,093
Related Allowance		740
Average Investment in Impaired Loans	24,615
Interest Income Recognized	176
Real Estate | Construction and development
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		4,648
Recorded Investment With No Allowance		4,466
Recorded Investment With Allowance		72
Total Recorded Investment		4,538
Related Allowance		4
Average Investment in Impaired Loans	1,920
Interest Income Recognized	14
Real Estate | Single family residential
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		19,466
Recorded Investment With No Allowance		15,139
Recorded Investment With Allowance		2,963
Total Recorded Investment		18,102
Related Allowance		42
Average Investment in Impaired Loans	13,703
Interest Income Recognized	98
Real Estate | Other commercial
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		10,645
Recorded Investment With No Allowance		4,713
Recorded Investment With Allowance		3,740
Total Recorded Investment		8,453
Related Allowance		694
Average Investment in Impaired Loans	8,992
Interest Income Recognized	64
Commercial
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		53,961
Recorded Investment With No Allowance		6,965
Recorded Investment With Allowance		29,114
Total Recorded Investment		36,079
Related Allowance		5,007
Average Investment in Impaired Loans	21,886
Interest Income Recognized	156
Commercial | Commercial
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		53,436
Recorded Investment With No Allowance		6,582
Recorded Investment With Allowance		28,998
Total Recorded Investment		35,580
Related Allowance		5,007
Average Investment in Impaired Loans	20,739
Interest Income Recognized	148
Commercial | Agricultural
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance		525
Recorded Investment With No Allowance		383
Recorded Investment With Allowance		116
Total Recorded Investment		499
Related Allowance		$ 0
Average Investment in Impaired Loans	1,147
Interest Income Recognized	$ 8

Loans and Allowance for Loan _8

Loans and Allowance for Loan Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020USD ($)loan	Mar. 31, 2019	Dec. 31, 2019USD ($)loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	0	0
Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	30		30
Troubled debt, balance | $	$ 5,233		$ 5,313
Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	12		12
Troubled debt, balance | $	$ 4,110		$ 4,411
Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	18		18
Troubled debt, balance | $	$ 1,123		$ 902
Real Estate | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	23		23
Troubled debt, balance | $	$ 2,403		$ 2,450
Real Estate | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	8		8
Troubled debt, balance | $	$ 1,353		$ 1,627
Real Estate | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	15		15
Troubled debt, balance | $	$ 1,050		$ 823
Real Estate | Construction and development | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	1		1
Troubled debt, balance | $	$ 71		$ 72
Real Estate | Construction and development | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	0		0
Troubled debt, balance | $	$ 0		$ 0
Real Estate | Construction and development | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	1		1
Troubled debt, balance | $	$ 71		$ 72
Real Estate | Single family residential | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	19		19
Troubled debt, balance | $	$ 1,802		$ 1,822
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	7		7
Troubled debt, balance | $	$ 898		$ 1,151
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	12		12
Troubled debt, balance | $	$ 904		$ 671
Real Estate | Other commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	3		3
Troubled debt, balance | $	$ 530		$ 556
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	1		1
Troubled debt, balance | $	$ 455		$ 476
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	2		2
Troubled debt, balance | $	$ 75		$ 80
Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	7		7
Troubled debt, balance | $	$ 2,830		$ 2,863
Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	4		4
Troubled debt, balance | $	$ 2,757		$ 2,784
Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	3		3
Troubled debt, balance | $	$ 73		$ 79
Commercial | Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	7		7
Troubled debt, balance | $	$ 2,830		$ 2,863
Commercial | Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	4		4
Troubled debt, balance | $	$ 2,757		$ 2,784
Commercial | Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	3		3
Troubled debt, balance | $	$ 73		$ 79

Loans and Allowance for Loan _9

Loans and Allowance for Loan Losses - Loans by Credit Risk Rating, Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	$ 3,861
2019	63,661
2018	38,126
2017	33,137
2016	22,153
2015 and Prior	37,205
Lines of Credit Amortized Cost Basis	138,142
Lines of Credit Converted to Term Loans Amortized Cost Basis	1,989
Total	338,274	$ 14,425,704
Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		14,113,275
Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		102,618
Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		209,421
Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		173
Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		217
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total		454,496
Consumer | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		451,829
Consumer | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,667
Consumer | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	1,191
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	1,191	204,802
Consumer | Credit cards | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		204,161
Consumer | Credit cards | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Credit cards | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		641
Consumer | Credit cards | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Credit cards | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	47
2019	1,256
2018	733
2017	1,634
2016	1,385
2015 and Prior	311
Lines of Credit Amortized Cost Basis	306
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	5,672	249,694
Consumer | Other consumer | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		247,668
Consumer | Other consumer | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Other consumer | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,026
Consumer | Other consumer | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer | Other consumer | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total		10,884,524
Real Estate | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		10,691,728
Real Estate | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		75,864
Real Estate | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		116,765
Real Estate | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		130
Real Estate | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		37
Real Estate | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	3,614
2018	639
2017	2,163
2016	453
2015 and Prior	626
Lines of Credit Amortized Cost Basis	2,401
Lines of Credit Converted to Term Loans Amortized Cost Basis	209
Total	10,105	2,236,861
Real Estate | Construction and development | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,229,019
Real Estate | Construction and development | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	45
2018	19
2017	1,957
2016	21
2015 and Prior	0
Lines of Credit Amortized Cost Basis	0
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	2,042	70
Real Estate | Construction and development | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	3,569
2018	620
2017	206
2016	432
2015 and Prior	626
Lines of Credit Amortized Cost Basis	2,401
Lines of Credit Converted to Term Loans Amortized Cost Basis	209
Total	8,063	7,735
Real Estate | Construction and development | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	0
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	0	0
Real Estate | Construction and development | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		37
Real Estate | Single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	33
2019	6,787
2018	10,242
2017	7,042
2016	6,839
2015 and Prior	11,981
Lines of Credit Amortized Cost Basis	3,557
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	46,481	2,442,064
Real Estate | Single family residential | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,394,284
Real Estate | Single family residential | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		6,049
Real Estate | Single family residential | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		41,601
Real Estate | Single family residential | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		130
Real Estate | Single family residential | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Real Estate | Other commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	3,765
2019	39,688
2018	19,327
2017	5,354
2016	11,705
2015 and Prior	23,438
Lines of Credit Amortized Cost Basis	50,029
Lines of Credit Converted to Term Loans Amortized Cost Basis	1,037
Total	154,343	6,205,599
Real Estate | Other commercial | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		6,068,425
Real Estate | Other commercial | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	1,037
2019	23,628
2018	2,116
2017	985
2016	4,845
2015 and Prior	3,379
Lines of Credit Amortized Cost Basis	12,477
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	48,467	69,745
Real Estate | Other commercial | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	2,728
2019	16,060
2018	17,211
2017	4,369
2016	6,860
2015 and Prior	20,059
Lines of Credit Amortized Cost Basis	37,552
Lines of Credit Converted to Term Loans Amortized Cost Basis	1,037
Total	105,876	67,429
Real Estate | Other commercial | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	0
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	0	0
Real Estate | Other commercial | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,810,970
Commercial | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,694,004
Commercial | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		26,754
Commercial | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		89,989
Commercial | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		43
Commercial | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		180
Commercial | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	16
2019	12,134
2018	7,008
2017	16,750
2016	1,671
2015 and Prior	841
Lines of Credit Amortized Cost Basis	80,411
Lines of Credit Converted to Term Loans Amortized Cost Basis	743
Total	119,574	2,495,516
Commercial | Commercial | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,384,263
Commercial | Commercial | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	209
2018	14
2017	270
2016	407
2015 and Prior	77
Lines of Credit Amortized Cost Basis	25,418
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	26,395	26,713
Commercial | Commercial | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	16
2019	11,925
2018	6,994
2017	16,480
2016	1,264
2015 and Prior	764
Lines of Credit Amortized Cost Basis	54,993
Lines of Credit Converted to Term Loans Amortized Cost Basis	743
Total	93,179	84,317
Commercial | Commercial | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	0
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	0	43
Commercial | Commercial | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		180
Commercial | Agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	182
2018	177
2017	194
2016	100
2015 and Prior	8
Lines of Credit Amortized Cost Basis	247
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	908	315,454
Commercial | Agricultural | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		309,741
Commercial | Agricultural | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	67
2018	0
2017	25
2016	12
2015 and Prior	0
Lines of Credit Amortized Cost Basis	17
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	121	41
Commercial | Agricultural | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	115
2018	177
2017	169
2016	88
2015 and Prior	8
Lines of Credit Amortized Cost Basis	230
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	787	5,672
Commercial | Agricultural | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	0
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	0	0
Commercial | Agricultural | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total		275,714
Other | Risk rate 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total		275,714
Other | Risk rate 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Other | Risk rate 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Other | Risk rate 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Other | Risk rate 8
Financing Receivable, Credit Quality Indicator [Line Items]
Total		$ 0
30-89 days past due | Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	866
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	866
30-89 days past due | Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	47
2019	1,109
2018	636
2017	1,188
2016	1,182
2015 and Prior	251
Lines of Credit Amortized Cost Basis	128
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	4,541
30-89 days past due | Real Estate | Single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	33
2019	4,672
2018	6,168
2017	4,648
2016	5,010
2015 and Prior	8,233
Lines of Credit Amortized Cost Basis	2,471
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	31,235
90 Days or More Past Due | Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Lines of Credit Amortized Cost Basis	325
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	325
90 Days or More Past Due | Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	147
2018	97
2017	446
2016	203
2015 and Prior	60
Lines of Credit Amortized Cost Basis	178
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	1,131
90 Days or More Past Due | Real Estate | Single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
2020 (YTD)	0
2019	2,115
2018	4,074
2017	2,394
2016	1,829
2015 and Prior	3,748
Lines of Credit Amortized Cost Basis	1,086
Lines of Credit Converted to Term Loans Amortized Cost Basis	0
Total	$ 15,246

Loans and Allowance for Loan_10

Loans and Allowance for Loan Losses - Collateral Dependent Loans (Details) $ in Thousands	Mar. 31, 2020USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	$ 75,670
Real Estate Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	23,648
Energy
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	43,573
Other Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	8,449
Real Estate | Construction and development
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	3,078
Real Estate | Construction and development | Real Estate Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	3,078
Real Estate | Construction and development | Energy
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Real Estate | Construction and development | Other Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Real Estate | Single family residential
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	3,586
Real Estate | Single family residential | Real Estate Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	3,586
Real Estate | Single family residential | Energy
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Real Estate | Single family residential | Other Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Real Estate | Other commercial
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	16,984
Real Estate | Other commercial | Real Estate Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	16,984
Real Estate | Other commercial | Energy
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Real Estate | Other commercial | Other Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Commercial | Commercial
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	52,022
Commercial | Commercial | Real Estate Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	0
Commercial | Commercial | Energy
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	43,573
Commercial | Commercial | Other Collateral
Loans and Leases Receivable Disclosure [Line Items]
Financing receivable, collateral dependent, amount	$ 8,449

Loans and Allowance for Loan_11

Loans and Allowance for Loan Losses - Activity in the Allowance for Loan Losses, by Portfolio Segment, for the Current Year (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit loss expense	$ 26,134	$ 9,285
Balance, end of period	243,195
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	68,244	56,694
Provision for credit loss expense	26,197	9,285
Charge-offs	(3,739)	(6,264)
Recoveries	1,116	840
Net charge-offs	(2,623)	(5,424)
Balance, end of period	243,195	60,555
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	2,169	2,419
Provision for credit loss expense	4,698	1,206
Charge-offs	(1,379)	(1,553)
Recoveries	443	300
Net charge-offs	(936)	(1,253)
Balance, end of period	18,029	2,372
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	22,863	20,514
Provision for credit loss expense	30,907	1,874
Charge-offs	(523)	(3,152)
Recoveries	347	158
Net charge-offs	(176)	(2,994)
Balance, end of period	76,327	19,394
Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	39,161	29,838
Provision for credit loss expense	(12,158)	5,307
Charge-offs	(396)	(417)
Recoveries	101	142
Net charge-offs	(295)	(275)
Balance, end of period	141,022	34,870
Loans, Excluding Acquired Loans | Credit Card | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	4,051	3,923
Provision for credit loss expense	2,750	898
Charge-offs	(1,441)	(1,142)
Recoveries	225	240
Net charge-offs	(1,216)	(902)
Balance, end of period	7,817	$ 3,919
Impact of CECL adoption | Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	151,377
Impact of CECL adoption | Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	12,098
Impact of CECL adoption | Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	22,733
Impact of CECL adoption | Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	114,314
Impact of CECL adoption | Loans, Excluding Acquired Loans | Credit Card | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 2,232

Right-Of-Use Lease Assets and_3

Right-Of-Use Lease Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Right-of-use lease assets	$ 38,345	$ 40,675
Lease liability included in other liabilities	$ 38,400	$ 40,900

Right-Of-Use Lease Assets and_4

Right-Of-Use Lease Assets and Lease Liabilities - Lease Expense and Supplemental Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease, expense	$ 3,200,500	$ 3,434,900
Weighted average remaining lease term	8 years 4 months 28 days	9 years 3 months 14 days
Weighted average discount rate	3.27%	3.46%

Premises and Equipment (Details

Premises and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Right-of-use lease assets	$ 38,345	$ 40,675
Accumulated depreciation and amortization	(127,827)	(119,865)
Total premises and equipment, net	484,990	492,384
Land
Property, Plant and Equipment [Line Items]
Premises and equipment	97,152	99,931
Buildings and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment	307,324	309,290
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment	102,342	99,343
Software
Property, Plant and Equipment [Line Items]
Premises and equipment	60,369	56,012
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 7,285	$ 6,998

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Textual (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Oct. 31, 2019	Oct. 30, 2019	Apr. 12, 2019
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 1,064,978	$ 1,055,520
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	10 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	15 years
Core Deposit Premium | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	10 years
Core Deposit Premium | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	15 years
Landrum Company
Finite-Lived Intangible Assets [Line Items]
Goodwill		131,300	$ 140,797	$ 407
Goodwill increase	$ 9,500
Reliance Bancshares, Inc.
Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 78,500			$ 78,493

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Changes in Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Jun. 30, 2019
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period	$ 127,340
Amortization of intangibles	(3,413)	$ (2,641)
Total	121,673		$ 127,340
Core deposit premiums, end of period	121,673		127,340
Core deposit intangible
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period	111,808	79,807	79,807
Acquisition of intangible asset	0		42,695
Disposition of intangible asset	(1,841)		0
Amortization of intangibles	(3,070)		(10,694)
Total	106,897	79,807	79,807
Core deposit premiums, end of period	106,897		111,808
Books of Business Intangible
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period	15,532	11,527	11,527
Acquisition of intangible asset	0		5,116
Disposition of intangible asset	(413)		0
Amortization of intangibles	(343)		(1,111)
Total	14,776	$ 11,527	15,532
Core deposit premiums, end of period	14,776		15,532
Landrum Company | Core deposit intangible
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period	24,300
Total	24,300		24,300
Core deposit premiums, end of period			24,300
Reliance Bancshares, Inc. | Core deposit intangible
Finite-lived Intangible Assets [Roll Forward]
Total				$ 18,400
Wealth Management Operations | Landrum Company | Core deposit intangible
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period	5,100
Total	$ 5,100		5,100
Core deposit premiums, end of period			$ 5,100

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Total	$ 121,673	$ 127,340
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	146,838	148,679
Accumulated amortization	(39,941)	(36,871)
Total	106,897	111,808	$ 79,807
Books of Business Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	19,938	20,350
Accumulated amortization	(5,162)	(4,818)
Total	$ 14,776	$ 15,532	$ 11,527

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2020	$ 10,120
2021	13,436
2022	13,384
2023	13,101
2024	12,199
Thereafter	59,433
Total	$ 121,673	$ 127,340

Time Deposits - Textual (Detail

Time Deposits - Textual (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Banking and Thrift [Abstract]
Time deposits certificates of $100,000 or more	$ 2,140	$ 2,150
Time deposits certificates over $250,000	$ 1,100	$ 837.3

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income taxes currently payable	$ 22,280	$ 10,317
Deferred income taxes	(1,586)	2,081
Provision for income taxes	$ 20,694	$ 12,398

Income Taxes - Tax Effects of T

Income Taxes - Tax Effects of Temporary Differences Related to Deferred Taxes Included in Other Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Loans acquired	$ 16,606	$ 20,783
Allowance for credit losses	60,678	16,732
Valuation of foreclosed assets	2,636	2,626
Tax NOLs from acquisition	17,467	18,118
Deferred compensation payable	2,866	2,750
Accrued equity and other compensation	5,914	6,677
Acquired securities	0	3,393
Right-of-use lease liability	9,646	10,221
Allowance for unfunded commitments	7,376	0
Other	5,414	7,886
Gross deferred tax assets	128,603	89,186
Deferred tax liabilities:
Goodwill and other intangible amortization	(40,378)	(41,221)
Accumulated depreciation	(36,731)	(36,554)
Right-of-use lease asset	(9,620)	(10,176)
Unrealized gain on available-for-sale securities	(11,725)	(3,720)
Deferred loan fees and costs	(2,994)	(3,018)
Acquired securities	(771)	0
Other	(5,332)	(4,633)
Gross deferred tax liabilities	(107,551)	(99,322)
Net deferred tax asset, included in other assets	$ 21,052
Net deferred tax liability, included in other assets		$ 10,136

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 20,560	$ 12,620
State income taxes, net of federal tax benefit	2,063	1,345
Discrete items related to ASU 2016-09	26	(26)
Tax exempt interest income	(1,421)	(961)
Tax exempt earnings on BOLI	(319)	(179)
Federal tax credits	(1,034)	(729)
Other differences, net	819	328
Provision for income taxes	$ 20,694	$ 12,398

Income Taxes - Textual (Details

Income Taxes - Textual (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
U.S. federal | Earliest Tax Year
Operating Loss Carryforwards [Line Items]
Open tax year	2016
State | Earliest Tax Year
Operating Loss Carryforwards [Line Items]
Open tax year	2016
Metropolitan
Operating Loss Carryforwards [Line Items]
Net operating losses		$ 80.9
Reliance Bancshares, Inc.
Operating Loss Carryforwards [Line Items]
Net operating losses			$ 49.5

Securities Sold Under Agreeme_3

Securities Sold Under Agreements to Repurchase - Textual (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Banking and Thrift [Abstract]
Repurchase agreements	$ 334.1	$ 133.2

Securities Sold Under Agreeme_4

Securities Sold Under Agreements to Repurchase - Contractual Maturity of the Agreements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	$ 334,100	$ 133,200
U.S. Government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	334,064	133,220
U.S. Government agencies | Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	334,064	133,220
U.S. Government agencies | Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	0	0
U.S. Government agencies | 30-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	0	0
U.S. Government agencies | Greater than 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	$ 0	$ 0

Other Borrowings and Subordin_3

Other Borrowings and Subordinated Notes and Debentures - Debt Components (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total other borrowings and subordinated debt		$ 1,785,225	$ 1,685,859
Total other borrowings
Debt Instrument [Line Items]
Total other borrowings and subordinated debt		1,396,829	1,297,599
FHLB advances, net of discount, due 2020 to 2034, 0.23% to 7.37% secured by real estate loans
Debt Instrument [Line Items]
Total other borrowings and subordinated debt		$ 1,362,295	1,262,691
FHLB advances, net of discount, due 2020 to 2034, 0.23% to 7.37% secured by real estate loans | Minimum
Debt Instrument [Line Items]
Fixed rate (as percent)		0.23%
FHLB advances, net of discount, due 2020 to 2034, 0.23% to 7.37% secured by real estate loans | Maximum
Debt Instrument [Line Items]
Fixed rate (as percent)		7.37%
Other long-term debt
Debt Instrument [Line Items]
Total other borrowings and subordinated debt		$ 34,534	34,908
Total subordinated notes and debentures
Debt Instrument [Line Items]
Total other borrowings and subordinated debt		388,396	388,260
Unamortized debt issuance costs		$ (2,916)	(3,008)
Subordinated Notes
Debt Instrument [Line Items]
Fixed rate (as percent)	5.00%	5.00%
Subordinated Notes | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)	2.15%
Subordinated Notes | Subordinated notes payable, due 4/1/2028, fixed-to-floating rate (fixed rate of 5.00% through 3/31/2023, floating rate of 2.15% above the three month LIBOR rate, reset quarterly)
Debt Instrument [Line Items]
Long-term debt, gross		$ 330,000	330,000
Subordinated Notes | Subordinated notes payable, due 4/1/2028, fixed-to-floating rate (fixed rate of 5.00% through 3/31/2023, floating rate of 2.15% above the three month LIBOR rate, reset quarterly) | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		2.15%
Subordinated Notes | Trust preferred securities, net of discount, due 9/15/2037, floating rate of 1.37% above the three month LIBOR rate, reset quarterly
Debt Instrument [Line Items]
Long-term debt, gross		$ 10,310	10,310
Subordinated Notes | Trust preferred securities, net of discount, due 9/15/2037, floating rate of 1.37% above the three month LIBOR rate, reset quarterly | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		1.37%
Subordinated Notes | Trust preferred securities, net of discount, due 6/6/2037, floating rate of 1.57% above the three month LIBOR rate, reset quarterly, callable without penalty
Debt Instrument [Line Items]
Long-term debt, gross		$ 10,310	10,310
Subordinated Notes | Trust preferred securities, net of discount, due 6/6/2037, floating rate of 1.57% above the three month LIBOR rate, reset quarterly, callable without penalty | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		1.57%
Subordinated Notes | Trust preferred securities, due 12/15/2035, floating rate of 1.45% above the three month LIBOR rate, reset quarterly, callable without penalty
Debt Instrument [Line Items]
Long-term debt, gross		$ 6,702	6,702
Subordinated Notes | Trust preferred securities, due 12/15/2035, floating rate of 1.45% above the three month LIBOR rate, reset quarterly, callable without penalty | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		1.45%
Subordinated Notes | Trust preferred securities, net of discount, due 6/15/2037, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty
Debt Instrument [Line Items]
Long-term debt, gross		$ 25,054	25,015
Subordinated Notes | Trust preferred securities, net of discount, due 6/15/2037, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		1.85%
Subordinated Notes | Trust preferred securities, net of discount, due 12/15/2036, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty
Debt Instrument [Line Items]
Long-term debt, gross		$ 3,009	3,004
Subordinated Notes | Trust preferred securities, net of discount, due 12/15/2036, floating rate of 1.85% above the three month LIBOR rate, reset quarterly, callable without penalty | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		1.85%
Subordinated Notes | Other subordinated debentures, due 12/31/2036, floating rate of prime rate minus 1.1%, reset quarterly | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)		1.10%
Unsecured Debt | Other subordinated debentures, due 12/31/2036, floating rate of prime rate minus 1.1%, reset quarterly
Debt Instrument [Line Items]
Long-term debt, gross		$ 5,927	$ 5,927

Other Borrowings and Subordin_4

Other Borrowings and Subordinated Notes and Debentures - Textual (Details) - USD ($)	1 Months Ended	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2020	Dec. 31, 2019	Oct. 31, 2019	Oct. 30, 2019	Dec. 31, 2017
Short-term Debt [Line Items]
FHLB advances outstanding		$ 1,350,000,000
FHLB advances		1,360,000,000
Additional advances from FHLB		2,100,000,000
Debt Instrument [Line Items]
Mortgage loans and investment securities securing FHLB advances		5,400,000,000
Assets		$ 20,841,352,000	$ 21,259,143,000			$ 15,000,000,000
Subordinated debt
Debt Instrument [Line Items]
Subordinated debentures	$ 330,000,000
Fixed rate (as percent)	5.00%	5.00%
Debt issuance costs	$ 3,600,000
Subordinated debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)	2.15%
Federal Home Loan Bank Owns the Options (FOTO) Advances
Short-term Debt [Line Items]
FHLB advances outstanding		$ 1,300,000,000
Federal Home Loan Bank Owns the Options (FOTO) Advances | Minimum
Short-term Debt [Line Items]
Debt term		10 years
Federal Home Loan Bank Owns the Options (FOTO) Advances | Maximum
Short-term Debt [Line Items]
Debt term		15 years
Federal Home Loan Bank Advances
Short-term Debt [Line Items]
Debt term		1 year
Landrum Company
Debt Instrument [Line Items]
Subordinated debentures				$ 33,917,000	$ 34,794,000

Other Borrowings and Subordin_5

Other Borrowings and Subordinated Notes and Debentures - Aggregate Annual Maturities of Long-term Debt (Details) $ in Thousands	Mar. 31, 2020USD ($)
Debt Disclosure [Abstract]
Remainder of 2020	$ 2,946
2021	3,016
2022	2,187
2023	2,366
2024	2,446
Thereafter	422,264
Total	$ 435,225

Capital Stock - Textual (Detail

Capital Stock - Textual (Details) - USD ($)	Oct. 29, 2019	May 07, 2020	Mar. 31, 2020	Mar. 31, 2019	Mar. 05, 2020	Dec. 31, 2019	Oct. 22, 2019	Jul. 23, 2012	Feb. 27, 2009
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)			40,040,000			40,040,000			40,040,000
Preferred stock, par value (in dollars per share)			$ 0.01			$ 0.01			$ 0.01
Preferred stock, shares issued (in shares)			767			767
Number of shares authorized to be repurchased (in shares)					180,000,000		60,000,000	1,700,000
Stock repurchases (in shares)			4,922,336	0
Stock repurchases, average price			$ 18.96
Maximum
Class of Stock [Line Items]
Preferred stock, liquidation preference, value									$ 80,000,000
Reliance Bancshares, Inc. | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	40,000
Preferred stock, par value (in dollars per share)	$ 0.01
Reliance Bancshares, Inc. | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	2,000.02
Preferred stock, par value (in dollars per share)	$ 0.01
Reliance Bancshares, Inc. | Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, dividend rate, percentage	7.00%
Reliance Bancshares, Inc. | Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	140
Preferred stock, shares issued (in shares)	0
Reliance Bancshares, Inc. | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.01
Subsequent Event
Class of Stock [Line Items]
Stock repurchases (in shares)		0

Undivided Profits - Textual (De

Undivided Profits - Textual (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Equity [Abstract]
Threshold percentage of net profits exceeded by dividends declared, any calendar year (as percent)	75.00%
Threshold percentage of net profits exceeded by dividends declared, combined with preceding year (as percent)	75.00%
Statutory accounting practices, statutory amount available for dividend payments without regulatory approval	$ 222.5
Tier 1 leverage capital required to be well capitalized to average assets (as percent)	5.00%
Tier 1 risk-based capital required to be well capitalized to risk weighted assets (as percent)	8.00%
Capital required to be well-capitalized to risk weighted assets (as percent)	10.00%
Common equity Tier 1 ratio required to be well capitalized (as percent)	6.50%
Capital conservation buffer phase in amount	0.625%
Capital conservation buffer phase in period	4 years
Capital conservation buffer (as percent)	2.50%
CET1 ratio (as percent)	11.10%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Compensation Plans (Details)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Stock Options Outstanding
Stock options outstanding, number of shares, balance (in shares) | shares	692,000
Stock options exercised, exercised (in shares) | shares	(1,000)
Stock options outstanding, number of shares, balance (in shares) | shares	691,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Stock options, weighted average exercise price, balance (in dollars per share) | $ / shares	$ 22.46
Stock options, weighted average exercise price, exercised (in dollars per share) | $ / shares	10.71
Stock options, weighted average exercise price, balance (in dollars per share) | $ / shares	$ 22.48
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Stock options outstanding, number of shares, exercisable (in shares) | shares	691,000
Stock options outstanding, weighted average exercise price, exercisable (in dollars per share) | $ / shares	$ 22.48
Non-vested Stock Awards Outstanding
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding, balance (in shares) | shares	21,000
Non-vested shares outstanding, vested (earned) (in shares) | shares	(4,000)
Non-vested shares outstanding, balance (in shares) | shares	17,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding. weighted-average grant-date fair value, balance (in dollars per share) | $ / shares	$ 23.19
Non-vested shares outstanding. weighted-average grant-date fair value, vested (earned) (in dollars per share) | $ / shares	20.88
Non-vested shares outstanding. weighted-average grant-date fair value, balance (in dollars per share) | $ / shares	$ 23.75
Non-vested Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding, balance (in shares) | shares	1,152,000
Non-vested shares outstanding, granted (in shares) | shares	425,000
Non-vested shares outstanding, vested (earned) (in shares) | shares	(351,000)
Non-vested shares outstanding, forfeited/expired (in shares) | shares	(42,000)
Non-vested shares outstanding, balance (in shares) | shares	1,184,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding. weighted-average grant-date fair value, balance (in dollars per share) | $ / shares	$ 26.79
Non-vested shares outstanding. weighted-average grant-date fair value, granted (in dollars per share) | $ / shares	23.26
Non-vested shares outstanding. weighted-average grant-date fair value, vested (earned) (in dollars per share) | $ / shares	26.35
Non-vested shares outstanding. weighted-average grant-date fair value, forfeited/expired (in dollars per share) | $ / shares	27.01
Non-vested shares outstanding. weighted-average grant-date fair value, balance (in dollars per share) | $ / shares	$ 25.64

Stock-Based Compensation - St_2

Stock-Based Compensation - Stock Options (Details)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	$ 9.46
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 24.07
Options outstanding, number of shares (in shares) | shares	691,000
Options outstanding, weighted average remaining contractual life	4 years 3 months 25 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 22.48
Options exercisable, number of shares (in shares) | shares	691,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 22.48
Range 01
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	9.46
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 9.46
Options outstanding, number of shares (in shares) | shares	1,000
Options outstanding, weighted average remaining contractual life	1 year 9 months 18 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 9.46
Options exercisable, number of shares (in shares) | shares	1,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 9.46
Range 02
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	10.65
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 10.65
Options outstanding, number of shares (in shares) | shares	3,000
Options outstanding, weighted average remaining contractual life	2 years 9 months 29 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 10.65
Options exercisable, number of shares (in shares) | shares	3,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 10.65
Range 03
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	20.29
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 20.29
Options outstanding, number of shares (in shares) | shares	71,000
Options outstanding, weighted average remaining contractual life	3 years 8 months 4 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 20.29
Options exercisable, number of shares (in shares) | shares	71,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 20.29
Range 04
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	20.36
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 20.36
Options outstanding, number of shares (in shares) | shares	2,000
Options outstanding, weighted average remaining contractual life	4 years 7 months 17 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 20.36
Options exercisable, number of shares (in shares) | shares	2,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 20.36
Range 05
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	22.20
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 22.20
Options outstanding, number of shares (in shares) | shares	74,000
Options outstanding, weighted average remaining contractual life	3 years 10 months 17 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 22.20
Options exercisable, number of shares (in shares) | shares	74,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 22.20
Range 06
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	22.75
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 22.75
Options outstanding, number of shares (in shares) | shares	436,000
Options outstanding, weighted average remaining contractual life	4 years 4 months 20 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 22.75
Options exercisable, number of shares (in shares) | shares	436,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 22.75
Range 07
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	23.51
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 23.51
Options outstanding, number of shares (in shares) | shares	97,000
Options outstanding, weighted average remaining contractual life	4 years 9 months 25 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 23.51
Options exercisable, number of shares (in shares) | shares	97,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 23.51
Range 08
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, range of exercise prices, minimum (in dollars per share)	24.07
Options outstanding, range of exercise prices, maximum (in dollars per share)	$ 24.07
Options outstanding, number of shares (in shares) | shares	7,000
Options outstanding, weighted average remaining contractual life	5 years 5 months 15 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 24.07
Options exercisable, number of shares (in shares) | shares	7,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 24.07

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Company's Restricted Performance Stock Unit Activity (Details) - Restricted Stock Units (RSUs) shares in Thousands	3 Months Ended
	Mar. 31, 2020shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares outstanding, balance (in shares)	199
Granted (in shares)	116
Vested (earned) (in shares)	(80)
Forfeited (in shares)	(11)
Non-vested shares outstanding, balance (in shares)	224

Stock-Based Compensation - Text

Stock-Based Compensation - Textual (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement [Abstract]
Stock-based compensation expense	$ 4,506,000	$ 3,084,000
Unrecognized stock-based compensation expense related to stock options	0
Unrecognized stock-based compensation expense related to non-vested stock awards	$ 24,697,000
Period unrecognized expenses is expected to be recognized	2 years 2 months 12 days
Intrinsic value of stock options outstanding	$ 33,000
Intrinsic value of stock options exercisable	$ 33,000
Share price (in dollars per share)	$ 18.40
Stock options exercised	$ 8,000	$ 6,000
Stock options granted	0	0

Earnings Per Share ("EPS") (Det

Earnings Per Share ("EPS") (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 available to common stockholders	$ 77,223	$ 47,695
Average common shares outstanding (in shares)	112,888	92,520
Average potential dilutive common shares (in shares)	249	351
Average diluted common shares (in shares)	113,137	92,871
Basic earnings per share (in dollars per share)	$ 0.68	$ 0.52
Diluted earnings per share (in dollars per share)	$ 0.68	$ 0.51

Earnings Per Share ("EPS") - Te

Earnings Per Share ("EPS") - Textual (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from earnings per share calculation (in shares)	614,100	0

Additional Cash Flow Informat_3

Additional Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Significant Noncash Transactions [Line Items]
Interest paid	$ 39,388	$ 38,047
Income taxes paid (refunded)	92	(54)
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities (adoption of ASU 2016-02)	0	32,757
Transfers of loans to other assets held for sale	114,925	0
Transfers of deposits to other liabilities held for sale	58,405	0
Transfers of loans to foreclosed assets held for sale
Other Significant Noncash Transactions [Line Items]
Transfers of loans	508	569
Transfers of premises to foreclosed assets and other real estate owned
Other Significant Noncash Transactions [Line Items]
Transfers of loans	$ 3,120	$ 0

Other Income and Other Operat_3

Other Income and Other Operating Expenses - Textual (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Income and Expenses [Abstract]
Other income	$ 12,801	$ 4,156
Gain on sale of business	$ 5,900

Other Income and Other Operat_4

Other Income and Other Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Income and Expenses [Abstract]
Professional services	$ 5,829	$ 4,323
Postage	2,236	1,726
Telephone	2,185	1,619
Credit card expense	4,382	3,860
Marketing	4,385	3,057
Software and technology	6,415	4,496
Operating supplies	936	618
Amortization of intangibles	3,413	2,641
Branch right sizing expense	238	45
Other expense	8,769	7,677
Total other operating expenses	$ 38,788	$ 30,062

Commitments and Credit Risk - T

Commitments and Credit Risk - Textual (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Other Commitments [Line Items]
Outstanding letters of credit	$ 70,628,000	$ 71,074,000
Standby Letters of Credit
Other Commitments [Line Items]
Deferred revenue	$ 0	0
Minimum
Other Commitments [Line Items]
Term of letter of credit	9 months
Maximum
Other Commitments [Line Items]
Term of letter of credit	15 years
Credit card commitments
Other Commitments [Line Items]
Outstanding commitments	$ 618,583,000	634,788,000
Other loan commitments
Other Commitments [Line Items]
Outstanding commitments	$ 3,148,372,000	$ 3,991,931,000

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Assets Measure on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 2,466,640	$ 3,288,343
U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	424,989	449,729
U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	161,289	194,249
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,179,837	1,742,945
State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	678,243	880,524
Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	22,282	20,896
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets held for sale	115,315	260,332
Derivative asset	42,102	14,903
Other liabilities held for sale	(58,405)	(159,853)
Derivative liability	(42,482)	(12,650)
Fair Value, Measurements, Recurring | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	424,989	449,729
Fair Value, Measurements, Recurring | U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	161,289	194,249
Fair Value, Measurements, Recurring | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,179,837	1,742,945
Fair Value, Measurements, Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	678,243	880,524
Fair Value, Measurements, Recurring | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	22,282	20,896
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets held for sale	0	0
Derivative asset	0	0
Other liabilities held for sale	0	0
Derivative liability	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	424,989	449,729
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets held for sale	0	0
Derivative asset	42,102	14,903
Other liabilities held for sale	0	0
Derivative liability	(42,482)	(12,650)
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	161,289	194,249
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,179,837	1,742,945
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	678,243	880,524
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	22,282	20,896
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets held for sale	115,315	260,332
Derivative asset	0	0
Other liabilities held for sale	(58,405)	(159,853)
Derivative liability	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 0	$ 0

Fair Value Measurements - Textu

Fair Value Measurements - Textual (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Collateral dependent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loan, related allowance	$ 27,131,000	$ 1,297,000
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of financing receivable, held-for-sale	$ 0	$ 0

Fair Value Measurements - Fai_2

Fair Value Measurements - Fair Value of Financial Assets Measured on a Nonrecurring Basis (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent)	$ 38,901	$ 49,190
Foreclosed assets and other real estate owned	2,050	18,798
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent)	0	0
Foreclosed assets and other real estate owned	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent)	0	0
Foreclosed assets and other real estate owned	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent)	38,901	49,190
Foreclosed assets and other real estate owned	$ 2,050	$ 18,798

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values and Related Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$ 55,714	$ 41,855
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,737,199	996,623
Interest bearing balances due from banks - time	4,309	4,554
Held-to-maturity securities	53,968	40,927
Mortgage loans held for sale	49,984	58,102
Interest receivable	57,039	62,707
Loans, net	14,131,082	14,357,460
Federal funds purchased and securities sold under agreements to repurchase	377,859	150,145
Other borrowings	1,396,829	1,297,599
Subordinated notes and debentures	388,396	388,260
Interest payable	15,258	12,898
Carrying Amount | Non-interest bearing transaction accounts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	3,572,244	3,741,093
Carrying Amount | Interest bearing transaction accounts and savings deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	8,840,678	9,090,878
Carrying Amount | Time deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	3,146,811	3,276,969
Fair Value Measurements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,737,199	996,623
Interest bearing balances due from banks - time	4,309	4,554
Held-to-maturity securities	55,714	41,855
Mortgage loans held for sale	49,984	58,102
Interest receivable	57,039	62,707
Loans, net	14,160,286	14,290,188
Federal funds purchased and securities sold under agreements to repurchase	377,859	150,145
Other borrowings	1,411,137	1,298,011
Subordinated notes and debentures	407,301	397,088
Interest payable	15,258	12,898
Fair Value Measurements | Non-interest bearing transaction accounts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	3,572,244	3,741,093
Fair Value Measurements | Interest bearing transaction accounts and savings deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	8,840,678	9,090,878
Fair Value Measurements | Time deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	3,163,694	3,270,333
Fair Value Measurements | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,737,199	996,623
Interest bearing balances due from banks - time	0	0
Held-to-maturity securities	0	0
Mortgage loans held for sale	0	0
Interest receivable	0	0
Loans, net	0	0
Federal funds purchased and securities sold under agreements to repurchase	0	0
Other borrowings	0	0
Subordinated notes and debentures	0	0
Interest payable	0	0
Fair Value Measurements | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-interest bearing transaction accounts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Fair Value Measurements | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest bearing transaction accounts and savings deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Fair Value Measurements | Quoted Prices in Active Markets for Identical Assets (Level 1) | Time deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Fair Value Measurements | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Interest bearing balances due from banks - time	4,309	4,554
Held-to-maturity securities	55,714	41,855
Mortgage loans held for sale	0	0
Interest receivable	57,039	62,707
Loans, net	0	0
Federal funds purchased and securities sold under agreements to repurchase	377,859	150,145
Other borrowings	1,411,137	1,298,011
Subordinated notes and debentures	407,301	397,088
Interest payable	15,258	12,898
Fair Value Measurements | Significant Other Observable Inputs (Level 2) | Non-interest bearing transaction accounts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	3,572,244	3,741,093
Fair Value Measurements | Significant Other Observable Inputs (Level 2) | Interest bearing transaction accounts and savings deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	8,840,678	9,090,878
Fair Value Measurements | Significant Other Observable Inputs (Level 2) | Time deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Fair Value Measurements | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Interest bearing balances due from banks - time	0	0
Held-to-maturity securities	0	0
Mortgage loans held for sale	49,984	58,102
Interest receivable	0	0
Loans, net	14,160,286	14,290,188
Federal funds purchased and securities sold under agreements to repurchase	0	0
Other borrowings	0	0
Subordinated notes and debentures	0	0
Interest payable	0	0
Fair Value Measurements | Significant Unobservable Inputs (Level 3) | Non-interest bearing transaction accounts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Fair Value Measurements | Significant Unobservable Inputs (Level 3) | Interest bearing transaction accounts and savings deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Fair Value Measurements | Significant Unobservable Inputs (Level 3) | Time deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	$ 3,163,694	$ 3,270,333

Derivative Instruments Derivati

Derivative Instruments Derivative Instruments - Notional and Fair Value Amounts of Derivative Instruments (Details) - Interest Rate Swap - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative assets, notional amount	$ 440,119	$ 401,969
Derivative assets, fair value	42,102	14,903
Derivative liability, notional amount	449,613	387,075
Derivative liabilities, fair value	$ 42,482	$ 12,650

Derivative Instruments (Details

Derivative Instruments (Details)	Mar. 31, 2020USD ($)
Risk Participation Agreements
Derivatives, Fair Value [Line Items]
Derivative, notional amount	$ 52,700,000
Energy Related Derivative
Derivatives, Fair Value [Line Items]
Derivative assets, notional amount	10,700,000
Derivative liability, notional amount	10,700,000
Derivative, net fair value	$ 531,400

Recent Events - Textual (Detail

Recent Events - Textual (Details) $ in Millions	3 Months Ended		4 Months Ended
	Mar. 31, 2020financial_center	Mar. 31, 2019	May 05, 2020USD ($)
Subsequent Event [Line Items]
Number of financial centers | financial_center	240
Number of financial centers temporarily closed | financial_center	52
Number of Loans	0	0
COVID-19 Pandemic | Subsequent Event
Subsequent Event [Line Items]
Number of applications			7,600
Amount funded through CARES Act PPP | $			$ 978
Extended Maturity and Payment Deferral | COVID-19 Pandemic | Subsequent Event
Subsequent Event [Line Items]
Number of Loans			4,300
Loans modified, amount | $			$ 3,200