Entity tax identification number Entity Tax Identification Number Rollovers EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Total investments Total investments EBP, Investment, Fair Value Maximum Maximum [Member] Forfeited nonvested account, decrease from administrative expense EBP, Forfeited Nonvested Account, Decrease from Administrative Expense Legal Entity [Axis] Legal Entity [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] EBP, Description of Plan [Table] EBP, Description of Plan [Table] Mutual Funds Mutual Fund [Member] Benefits payable EBP, Liability to Participant EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Pretax, maximum annual compensation to total compensation, percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Maximum borrowing, amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Fair value measurements EBP, Investment, Fair Value and NAV [Text Block] Minimum borrowing, amount EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Investments at Fair Value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Retirement age EBP, Retirement Age EBP, Retirement Age Plan Interest EBP, Nonconsolidated, Plan Interest in Master Trust [Member] Level 1 Fair Value, Inputs, Level 1 [Member] EBP, Investment, Fair Value and NAV [Abstract] Assets: EBP, Asset [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Increases (Decreases): EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Payment of Benefits EBP, Payment to Participant [Policy Text Block] Transfers from other plans EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan EBP, Master Trust [Line Items] EBP, Master Trust [Line Items] Amendment Flag Amendment Flag EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Number of Shares/Units (in shares) EBP, Investment, Number of Shares EBP, Description of Plan and Accounting Change [Abstract] Receivables: EBP, Receivable [Abstract] Schedule of Classification of Investments at Fair Value by Classification EBP, Investment, Fair Value and NAV [Table Text Block] Investments [Domain] Investments [Domain] EBP, Master Trust [Abstract] EBP, Master Trust [Abstract] Use of Estimates EBP, Use of Estimate [Policy Text Block] Schedule H, Line 4i – Schedule of Assets (Held At End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] Requisite service period EBP, Requisite Service Period, Consecutive Months EBP, Requisite Service Period, Consecutive Months Risks and Uncertainties EBP, Risk and Uncertainty [Text Block] Company EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Minimum Minimum [Member] Investment Type [Axis] Investment Type [Axis] Interest income from participant loans EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution EBP, Number Of Investment Vehicles EBP, Number Of Investment Vehicles EBP, Number Of Investment Vehicles Participants EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover EBP 018 EBP 018 [Member] EBP 018 Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Change in net assets available for benefits EBP, Change in Net Asset Available for Benefit, Including Plan Transfers, Increase (Decrease) EBP, Change in Net Asset Available for Benefit, Including Plan Transfers, Increase (Decrease) Interest and dividends Investment Income EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Eligible compensation percentage EBP, Employer Contribution, Eligible Compensation, Percentage EBP, Employer Contribution, Eligible Compensation, Percentage EBP, Description of Plan [Line Items] EBP, Description of Plan [Line Items] Plan number EBP, Plan Number EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Description of Plan and Significant Accounting Policies EBP, Description of Plan [Text Block] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] Non-Union Employees Non-Union Employees [Member] Non-Union Employees EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Domain] EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Domain] Common stocks EBP, Employer, Common Stock [Member] EBP, Schedule of Asset Held for Investment [Abstract] Total increases EBP, Change in Net Asset Available for Benefit, Increase Requisite hours of service EBP, Requisite Hours Of Service EBP, Requisite Hours Of Service Qualified Non-Elective Contributions EBP, Qualified Non-Elective Contributions [Member] EBP, Qualified Non-Elective Contributions Document Information [Line Items] Document Information [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Table] EBP, Risk and Uncertainty [Table] A. O. Smith Corporation Master Trust EBP, Master Trust [Text Block] Participant compensation matched, percentage EBP, Employer Contribution, Participant Compensation Matched, Percentage EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Level 2 Fair Value, Inputs, Level 2 [Member] Equities Equity Securities [Member] Corporate Bonds Corporate Bond Securities [Member] Involuntary cash-out limit EBP, Involuntary Cash-out Limit EBP, Involuntary Cash-out Limit EBP, Tax Status [Table] EBP, Tax Status [Table] Change in net assets available before transfers EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Party-in-Interest and Related Party Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] Total receivables EBP, Receivable Text Block [Abstract] Company contributions EBP, Employer Contribution, Receivable Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Unrealized Gain (Loss) on Investment Union Employees Union Employees [Member] Union Employees Benefit and withdrawal payments EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Plan interest in A.O. Smith Corporation Master Trust at Fair Value EBP, Investment, Plan Interest in Master Trust, Fair Value EBP, Employer Contribution, Tranche Two EBP, Employer Contribution, Tranche Two [Member] EBP, Employer Contribution, Tranche Two Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Employer Matching Contribution EBP, Employer Matching Contribution [Member] EBP, Employer Matching Contribution EBP, Statement of Net Asset Available for Benefit [Abstract] Contributions, up to EBP, Participant Contribution, Before-Tax And After-Tax, Maximum Annual Contribution to Eligible Compensation, Percentage EBP, Participant Contribution, Before-Tax And After-Tax, Maximum Annual Contribution to Eligible Compensation, Percentage Annual non-elective employer contribution EBP, Employer Contribution, Annual Compensation To Total Compensation, Percentage EBP, Employer Contribution, Annual Compensation To Total Compensation, Percentage EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type Vesting percentage EBP, Employer Contribution Vesting Percentage Company contribution and/ or investment earning percentage vesting to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions, upon completion of minimum service period or attainment of maximum vesting age Change in plan interest in A.O. Smith Corporation Master Trust (Note 2) EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Change in Plan Interest in Master Trust Administrative Expenses EBP, Expense [Policy Text Block] Participant loan, current value EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Investment Valuation EBP, Investment [Policy Text Block] EBP, Master Trust [Table] EBP, Master Trust [Table] Participant contributions EBP, Participant Contribution, Receivable Total Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type Plan Termination EBP, Plan Termination [Text Block] Entity Central Index Key Entity Central Index Key Participant loan, interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate Common/Collective trusts Common Collective Trust [Member] Net assets available for benefits: EBP, Net Asset Available for Benefit [Abstract] EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] Cash Cash and Cash Equivalents [Member] Decreases: EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Administrative expenses EBP, Participant Paid Administrative Expenses EBP, Participant Paid Administrative Expenses Forfeited nonvested account, decrease from employer contribution EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Notes receivable from participants EBP, Note Receivable from Participant Master Trust EBP, Nonconsolidated, Master Trust [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Entity Registrant Name Entity Registrant Name Schedule of Master Trust Net Assets EBP, Master Trust [Table Text Block] EBP, Employer Contribution EBP, Employer Contribution [Member] EBP, Employer Contribution Reclassifications EBP, Reclassifications [Policy Text Block] EBP, Reclassifications Subsequent Events EBP, Subsequent Event [Policy Text Block] Income Tax Status EBP, Tax Status [Text Block] Period from commencement for lump sum distributions EBP, Participant Contributions, Withdrawal Period from Commencement EBP, Participant Contributions, Withdrawal Period from Commencement Maximum borrowing, to total account, percentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Vesting period EBP, Employer Contribution Vesting Service Period Minimum Vesting service period for company contribution and/ or investment earning to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions. Document Information [Table] Document Information [Table] Net income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Axis] EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Axis] Withdrawal service period EBP, Withdrawal Service Period EBP, Withdrawal Service Period EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Level 3 Fair Value, Inputs, Level 3 [Member] Contributions, not less than EBP, Participant Contribution, Before-Tax And After-Tax, Minimum Annual Contribution to Eligible Compensation, Percentage EBP, Participant Contribution, Before-Tax And After-Tax, Minimum Annual Contribution to Eligible Compensation, Percentage Net assets available for benefits Beginning of year End of year EBP, Net Asset Available for Benefit Entity [Domain] Entity [Domain] Contributions: EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Participant loan, cost EBP, Asset Held for Investment, Participant Loan, Cost EBP, Asset Held for Investment, Participant Loan, Cost Forfeited nonvested account EBP, Forfeited Nonvested Account Matching percentage EBP, Employer Contribution, Matching Percentage EBP, Employer Contribution, Tranche One EBP, Employer Contribution, Tranche One [Member] EBP, Employer Contribution, Tranche One NAV Fair Value Measured at Net Asset Value Per Share [Member] EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Table] Interest in PepsiCo Master Trust EBP, Interest in Master Trust, Percentage EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain]