Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Loans held for sale (includes $42 million at fair value as of Jun 30, 2026 and none at fair value as of Dec. 31, 2025) Loans held for sale Financing Receivable, Held-for-Sale Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Weighted Average Payment Delay (in months) Financing Receivable, Modified, Weighted Average Payment Delay From Modification Financing Receivable, Modified, Weighted Average Payment Delay From Modification Statistical Measurement [Domain] Statistical Measurement [Domain] Retail loan substandard period (in days) Retail Loan Downgraded To Substandard Delinquency status upon which a retail loan is downgraded to substandard Title of 12(b) Security Title of 12(b) Security Net income available to common shareholders Net Income (Loss) Available to Common Stockholders, Diluted Carrying Value Reported Value Measurement [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Document Fiscal Year Focus Document Fiscal Year Focus Merger-related expense Business Combination, Acquisition-Related Cost, Expense Schedule of Assets Measured at Fair Value on a Non-Recurring Basis Fair Value Measurements, Nonrecurring [Table Text Block] Commitments to land additional funds to TDRs Commitments To Lend Additional Funds To TDRs Commitments To Lend Additional Funds To TDRs Adjustment to Compensation, Amount Adjustment to Compensation Amount Pledged Status [Axis] Pledged Status [Axis] Financial Instrument [Axis] Financial Instrument [Axis] Financing Receivable, Nonaccrual [Table] Financing Receivable, Nonaccrual [Table] Financial liabilities Financial Liabilities Fair Value Disclosure [Abstract] Segment Reporting [Abstract] Schedule of Estimated Amortization Expense of Other Intangible Assets Intangible Asset, Finite-Lived, and Capitalized Cost, Software to be Sold, Leased, or Marketed, Estimated Amortization Expense [Table Text Block] Total deposits Deposits Deposits Common stock — $1.00 par value, Authorized — 360 million shares at Jun 30, 2026 and 180 million shares at Dec. 31, 2025, Issued and outstanding — 151 million shares at June 30, 2025 and 78 million at 
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Terry Turner [Member] M. Terry Turner Loss Contingencies [Table] Loss Contingencies [Table] Doubtful Doubtful [Member] Interest Rate Reduction Contractual Interest Rate Reduction [Member] Total non-interest revenue Business Combination, Pro Forma Information, Non-interest Income Business Combination, Pro Forma Information, Non-interest Income Total loans Total Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process Issuance of stock related to merger Stock Issued During Period, Value, Acquisitions Cash surrender value of bank-owned life insurance Business Combination, Recognized Asset Acquired, Cash Surrender Value Of Bank Owned Life Insurance Business Combination, Recognized Asset Acquired, Cash Surrender Value Of Bank Owned Life Insurance Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Prior Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal 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[Member] Residential Real Estate Residential Real Estate [Member] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Basic Net Income Per Common Share: Earnings Per Share, Basic [Abstract] 5 to 10 Years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Shareholders' Equity and Other Comprehensive Income (Loss) Equity [Text Block] Security Exchange Name Security Exchange Name Debt securities, available-for-sale, realized loss Gross realized losses on sales Debt Securities, Available-for-Sale, Realized Loss Amortized Cost Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss Bankers Healthcare Group, LLC Bankers Healthcare Group, LLC [Member] Bankers Healthcare Group, LLC Total Debt Securities, Held-to-Maturity, Amortized Cost Excluding Accrued Interest, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date Equity Method 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reclassified from AOCI Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Newco Steel Newco Inc. [Member] Steel Newco Inc. Allowance for credit loss, reasonable and supportable forecast period (in year) Financing Receivable, Allowance For Credit Loss, Reasonable And Supportable Forecast Period Financing Receivable, Allowance For Credit Loss, Reasonable And Supportable Forecast Period Deposits Interest Expense, Deposits Within One Year Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Net change OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Diluted Net Income Per Common Share: Earnings Per Share, Diluted [Abstract] 1 to 5 Years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Retail loan charge off (in days) Retail Loan Charge Off Delinquency status upon which a retail loan will be charged off in its entirety. 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[Table Text Block] Securities purchased with agreement to resell Securities Purchased under Agreements to Resell Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Total preliminary consideration Business Combination, Consideration Transferred Additional Paid-in Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Unrealized loss on securities Total, fair value Debt Securities, Available-for-Sale, Unrealized Loss Position Allowance for credit loss, measurement input, estimated peak weighted average unemployment rate (in percent) Financing Receivable, Allowance For Credit Loss, Measurement Input, Estimated Weighted Average Unemployment Rate Financing Receivable, Allowance For Credit Loss, Measurement Input, Estimated Weighted Average Unemployment Rate Name Trading Arrangement, Individual Name Financing Receivable, Nonaccrual [Line Items] Financing Receivable, Nonaccrual [Line Items] Wealth management revenue Wealth Management Revenue Wealth Management Revenue Land and development Land Acquisition [Member] Land Acquisition [Member] Pre-tax income (loss) recognized on cash flow hedges Gain (Loss) on Derivative Instruments, Net, Pretax Investment securities gains (losses), net Debt and Equity Securities, Gain (Loss) Company Selected Measure Amount Company Selected Measure Amount Financial Asset, Period Past Due [Axis] Financial Asset, Aging [Axis] Dividends received from equity method investment Proceeds from Equity Method Investment, Distribution Derivatives Not Designated as Hedging Instruments Not Designated as Hedging Instruments Not Designated as Hedging Instrument [Member] Investments, Debt and Equity Securities [Abstract] Equity Method Investments and Joint Ventures [Abstract] Deposits: Deposits [Abstract] Total net gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to assets still held Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Allowance for loan losses: Allowance for Loan and Lease Losses [Roll Forward] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Non-PEO NEO Non-PEO NEO [Member] Wealth Wealth Wealth Reporting [Member] Wealth Reporting Entity Address, Address Line One Entity Address, Address Line One Investment securities HTM, Fair value Debt Securities, Held-to-Maturity, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract] Income tax expense Income Tax Expense (Benefit) Total non-interest expense Noninterest Expense Gain (loss) on fair value hedges recognized on termination Gain (Loss) on Fair Value Hedges Recognized in Earnings Fair Value Hedges Fair Value Hedging [Member] Award Timing Method Award Timing Method [Text Block] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Consolidation Consolidation, Policy [Policy Text Block] Increase (decrease) in cash and cash equivalents including restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Total Charge-offs Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] Accrued interest receivable on investment securities available for sale Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Net income Net income Net Income (Loss) Attributable to Parent Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Loan Restructuring Modification [Domain] Loan Restructuring Modification [Domain] Debt security, premium Debt Securities, Held-To-Maturity, Discount (Premium) Debt Securities, Held-To-Maturity, Discount (Premium) Statement [Table] Statement [Table] Restatement Determination Date: Restatement Determination Date [Axis] Other consumer loans Other Consumer Loans [Member] Other Consumer Loans [Member] Term loans amortized cost basis by origination, before current fiscal year Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year Schedule of Current, Accruing Past Due, and Non-Accrual Loans by Portfolio Class Financing Receivable, Nonaccrual [Table Text Block] Liabilities assumed: Business Combination, Recognized Liability Assumed, Liability [Abstract] Loans held for sale Business Combination, Recognized Asset Acquired, Loans Held For Sale Business Combination, Recognized Asset Acquired, Loans Held For Sale Reclassification adjustment for accretion of unrealized holding gains on HTM securities, net of tax OCI, Debt Securities, Available-for-Sale, Transfer to Held-to-Maturity, Adjustment from AOCI for Amortization of Gain (Loss), after Tax Loans held-for-sale, fair value disclosure Loan, Held-for-Sale, Fair Value Disclosure Interest income: Revenues [Abstract] Corporate notes and other Corporate Notes And Other Securities [Member] Corporate Notes And Other Securities Basis of Presentation and Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract]