Pooled Separate Accounts Prin Core Plus Bond Sep Acct-Z [Member] Principal Core Plus Bond Separate Account [Member] Principal Core Plus Bond Separate Account. Statistical Measurement [Domain] Statistical Measurement [Domain] Exempt Party-In-Interest Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] Interest on notes receivable from participants Interest income on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Document Information [Line Items] Document Information [Line Items] Maximum amount available to Participants as a loan EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Participant contribution receivables EBP, Participant Contribution, Receivable Participant Contribution Receivables EBP, Contribution [Policy Text Block] EBP, Description of Plan and Accounting Change [Abstract] Investment Type [Axis] Investment Type [Axis] Rollover contributions EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Pooled Separate Accounts Prin Equity Income SA-Z [Member] Principal Equity Income Separate Account [Member] Principal Equity Income Separate Account. Amount available to Participants as a loan, Percentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Income Tax Status of Plan EBP, Tax Status [Text Block] Common/Collective Trust PRIN LIFETIME HYBR 2060 CIT Z [Member] Principal Lifetime Hybrid 2060 Fund [Member] Principal Lifetime Hybrid 2060 Fund. Total liabilities EBP, Liability EBP, Description of Plan [Line Items] EBP, Description of Plan [Line Items] Interest and dividends EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Fully Benefit-Responsive Investment Contracts EBP, Fully Benefit-Responsive Investment Contract [Text Block] Common/Collective Trust PRIN LIFETIME HYBR 2030 CIT Z [Member] Principal Lifetime Hybrid 2030 Fund [Member] Principal Lifetime Hybrid 2030 Fund. Pooled Separate Accounts Prin Diversified Intl SA-Z [Member] Principal Diversified International Separate Account [Member] Principal Diversified International Separate Account. EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Newmark Group, Inc. [Member] Company [Member] Company. Participant Loans, Current Value EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Fair Value Measurements EBP, Investment, Fair Value and NAV [Text Block] Minimum service period of employee for Plan eligibility, in hours EBP Minimum Service Period of Employee for Plan Eligibility in Hours EBP Minimum Service Period of Employee for Plan Eligibility in Hours. Registered Investment Company PRINCIPAL GOV MONEY MKT R6 FD [Member] Principal Government Money Market R6 Fund [Member] Principal Government Money Market R6 Fund. EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Table] Total contribution to the plan, noncash EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Noncash Management Fees and Operating Expenses EBP, Expense [Policy Text Block] Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Registered Investment Company DFA EMERG MKT CORE EQTY 2 I FD [Member] Registered Investment Dfa Emerg Mkt [Member] Registered Investment Dfa Emerg Mkt Core Eqty 21 Fd. Minimum amount available to Participants as a loan EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Common/Collective Trust PRIN LIFETIME HYBR 2015 CIT Z [Member] Principal Lifetime Hybrid 2015 Fund [Member] Principal Lifetime Hybrid 2015 Fund. MFS Investment Management [Member] MFS Investment Management [Member] MFS Investment Management. EBP, Fully Benefit-Responsive Investment Contract [Table] EBP, Fully Benefit-Responsive Investment Contract [Table] EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Registered Investment Company PUTNAM SM CAP GROWTH R6 FUND [Member] Putnam Small Cap Growth R6 Fund [Member] Putnam Small Cap Growth R6 Fund. Newmark Fund Company Fund [Member] Company Fund. Distributions to participants EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Employer contribution receivables EBP, Employer Contribution, Receivable Participant contributions EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Account vesting percentage of employees if Plan is terminated Employee Benefit Plan Account Vesting Percentage if Plan is Terminated Employee Benefit Plan Account Vesting Percentage if Plan is Terminated. Maximum catch-up contributions allowed Employee Benefit Plan Change in Net Asset Available for Benefit Increase for Catch up Contributions Employee Benefit Plan Change in Net Asset Available for Benefit Increase for Catch up Contributions. EBP, Investment, Current Value, Type [Extensible Enumeration] EBP, Investment, Current Value, Type [Extensible Enumeration] Registered Investment Company Vgd LT Inv-Grade Bond Adm Fund [Member] Vanguard Long Term Investment Grade Bond Admiral Fund [Member] Vanguard Long Term Investment Grade Bond Admiral Fund. Vanguard Group - Registered Investment Company Vanguard Sm Cap Index Adm Fund [Member] Vanguard Small Cap Index Admiral Fund [Member] Vanguard Small Cap Index Admiral Fund. Benefit Payments to Participants and Beneficiaries EBP, Payment to Participant [Policy Text Block] Employer contributions Total contribution to the plan EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash Net assets available for benefits Net assets available for benefits, beginning of period Net assets available for benefits, end of period EBP, Net Asset Available for Benefit EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] EBP, Fully Benefit-Responsive Investment Contract [Line Items] EBP, Fully Benefit-Responsive Investment Contract [Line Items] Registered Investment Company Vanguard Mid Cap Index Adm Fd [Member] Vanguard Mid Cap Index Admiral Fund [Member] Vanguard Mid Cap Index Admiral Fund. Common/Collective Trust PRIN LIFETIME HYBR INC CIT Z [Member] Principal Lifetime Hybrid Income Fund [Member] Principal Lifetime Hybrid Income Fund. Total assets EBP, Asset Common/Collective Trust PRIN LIFETIME HYBR 2020 CIT Z [Member] Principal Lifetime Hybrid 2020 Fund [Member] Principal Lifetime Hybrid 2020 Fund. Participant loans and accrued interest on participant loans EBP Participant Loans and Accrued Interest on Participant Loans. EBP Participant Loans and Accrued Interest on Participant Loans. Total other income Employee Benefit Plan Change in Net Asset Available for Benefit Increase for Other Income Employee Benefit Plan Change in Net Asset Available for Benefit Increase for Other Income. Employer Security Newmark Group, Inc. Stock [Member] Employer Security Stock [Member] Employer Security Stock. Maximum combined amount of participant's pre-tax and Roth contributions EBP, Participant Contribution, Pretax, Maximum Annual Compensation, Amount Registered Investment Company Fidelity 500 Index Fund [Member] Fidelity 500 Index Fund [Member] Fidelity 500 Index Fund. Automatic enrollment contribution percentage EBP, Participant Contribution, Automatic, Deferral Rate Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] EBP, Tax Status [Abstract] Net increase in net assets available for benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Cover [Abstract] Putnam Investments [Member] Putnam Investments [Member] Putnam Investments. Maximum Maximum [Member] Total contribution to the plan, cash EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Assets: EBP, Asset [Abstract] Minimum Minimum [Member] Pretax and Roth contribution, maximum percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage EBP, Schedule of Asset Held for Investment [Abstract] Entity [Domain] Entity Entity [Domain] Investment and Participant Loans, Current Value EBP, Asset Held for Investment Investment, Identifier [Axis] Investment, Identifier [Axis] Initial funding transferred to the plan EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan EBP, Tax Determination Letter, Obtained [true false] EBP, Tax Determination Letter, Obtained [true false] EBP, Investment, Fair Value and NAV [Abstract] Fidelity Investments [Member] Fidelity Investments [Member] Fidelity Investments. Basis of Accounting EBP, Basis of Accounting [Policy Text Block] EBP, Subsequent Event [Line Items] EBP, Subsequent Event [Line Items] Goldman Sachs [Member] Goldman Sachs [Member] Goldman Sachs. EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] Common/Collective Trust PRIN LIFETIME HYBR 2025 CIT Z [Member] Principal Lifetime Hybrid 2025 Fund [Member] Principal Lifetime Hybrid 2025 Fund. EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Pooled Separate Accounts Prin Real Estate Secs SA-Z [Member] Principal Real Estate Securities Separate Account [Member] Principal Real Estate Securities Separate Account. BlackRock [Member] BlackRock [Member] BlackRock. Mutual Funds Mutual Fund [Member] EBP, Description of Plan [Table] EBP, Description of Plan [Table] EBP, Asset Held for Investment, Party-in-Interest [true false] EBP, Asset Held for Investment, Party-in-Interest [true false] Registered Investment Company Vanguard Ttl Bd Mkt Idx Inst [Member] Vanguard Ttl Bond Market Institutional Fund [Member] Vanguard Ttl Bond Market Institutional Fund. Elected Participants age for receipt of distribution EBP Elected Participants Age to Get Deferred Receipt of Distribution EBP Elected Participants Age to Get Deferred Receipt of Distribution. Investment Valuation and Income Recognition EBP, Investment [Policy Text Block] Participant-directed investments at contract value EBP, Investment, Excluding Plan Interest in Master Trust, Contract Value Amendment Flag Amendment Flag Registered Investment Company MFS Mid Cap Value R6 Fund [Member] MFS Mid Cap Value R6 Fund [Member] MFS Mid Cap Value R6 Fund. Registered Investment Company Vanguard Intl Growth Adm Fd [Member] Vanguard International Growth Admiral Fund [Member] Vanguard International Growth Admiral Fund. Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Common/Collective Trust Funds Common Collective Trust [Member] Registered Investment Company BlackRock Md-Cp Gr Eq K Fd [Member] Black Rock Md Cp Gr Eq K Fund [Member] Black Rock Md Cp Gr Eq K Fund. Fair Value of the Plan's Investments EBP, Investment, Fair Value and NAV [Table Text Block] Total deductions EBP, Change in Net Asset Available for Benefit, Decrease Current Value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Pooled Separate Accounts Prin Blue Chip SA-Z [Member] Principal Blue Chip Separate Account [Member] Principal Blue Chip Separate Account. EBP, Subsequent Event [Table] EBP, Subsequent Event [Table] EBP, Related Party and Party-in-Interest Transactions [Abstract] Maximum account balance for participant to get distribution Maximum Vested Account Balance Required for Participant to Get Distribution Maximum Vested Account Balance Required for Participant to Get Distribution. EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Contributions: EBP, Contribution [Abstract] Minimum age for Plan eligibility EBP Minimum Age for Plan Eligibility Employee Benefit Plan Minimum Age for Plan Eligibility. EBP, Statement of Net Asset Available for Benefit [Abstract] Description of Plan EBP, Description of Plan [Text Block] Investment, Issuer Name [Axis] Investment, Issuer Name [Axis] Tax determination letter date EBP, Tax Determination Letter, Date Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Notes Receivable from Participants EBP, Note Receivable from Participant [Policy Text Block] Total additions EBP, Change in Net Asset Available for Benefit, Increase EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items] Entity Central Index Key Entity Central Index Key Participant Loans, Interest Rate EBP, Asset Held for Investment, Participant Loan, Interest Rate Crediting rate by the contract issuer Employee Benefit Plan Fully Benefit Responsive Investment Contract Crediting Rate Employee Benefit Plan Fully Benefit Responsive Investment Contract Crediting Rate. Participant-directed investments at fair value Total investments EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Legal Entity [Axis] Legal Entity Legal Entity [Axis] Entity tax identification number Entity Tax Identification Number Pooled Separate Accounts EBP, Pooled Separate Account [Member] Net investment gain EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Common/Collective Trust PRIN LIFETIME HYBR 2040 CIT Z [Member] Principal Lifetime Hybrid 2040 Fund [Member] Principal Lifetime Hybrid 2040 Fund. EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Minimum service period for Plan eligibility EBP Minimum Service Period for Plan Eligibility EBP Minimum Service Period for Plan Eligibility. Plan number EBP, Plan Number EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] Investment, Issuer Name [Domain] Investment, Issuer Name [Domain] EBP, Investment, Issuer Name [Extensible Enumeration] EBP, Investment, Issuer Name [Extensible Enumeration] Document Type Document Type Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] Principal Funds Inc [Member] Principal Funds Inc. [Member] Principal Funds Inc. EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Common/Collective Trust PRIN LIFETIME HYBR 2050 CIT Z [Member] Principal Lifetime Hybrid 2050 Fund [Member] Principal Lifetime Hybrid 2050 Fund. Registered Investment Company Goldman Sch Sm Cp Vl Ins R6 Fd [Member] Goldman Sachs Small Cap Value Institutional R6 Fund [Member] Goldman Sachs Small Cap Value Institutional R6 Fund. Use of Estimates EBP, Use of Estimate [Policy Text Block] Common/Collective Trust PRIN LIFETIME HYBR 2065 CIT Z [Member] Principal Lifetime Hybrid 2065 Fund [Member] Principal Lifetime Hybrid 2065 Fund. EBP, Fully Benefit-Responsive Investment Contract [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Deductions: EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Pretax and Roth contribution, minimum percentage EBP Participation Minimum Pretax Contribution of Annual Compensation Percentage EBP Participation Minimum Pretax Contribution of Annual Compensation Percentage. Common/Collective Trust PRIN LIFETIME HYBR 2035 CIT Z [Member] Principal Lifetime Hybrid 2035 Fund [Member] Principal Lifetime Hybrid 2035 Fund. Dimensional Fund Advisors [Member] Dimensional Fund Advisors [Member] Dimensional Fund Advisors. Notes receivable from participants EBP, Note Receivable from Participant Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Form 5500, Schedule H, Part IV, Line 4(i) - Schedule of Assets (Held at End of Year) EBP, Schedule of Asset Held for Investment [Table Text Block] Additions: EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Principal Life Insurance Company [Member] Principal Life Insurance Company [Member] Principal Life Insurance Company. Other Income: Employee Benefit Plan Change in Net Asset Available for Benefit Increase Decrease Other Income Loss [Abstract] Employee Benefit Plan Change in Net Asset Available for Benefit Increase Decrease Other Income Loss. Principal Global Investors Trust Company [Member] Principal Global Investors Trust Company [Member] Principal Global Investors Trust Company. EBP, Accounting Policy [Table] EBP, Accounting Policy [Table] Investments [Domain] Investments [Domain] EBP, Subsequent Event [Abstract] Defined contribution plan matching eligible participant, description Defined Contribution Plan Matching Eligible Participant Description Defined Contribution Plan Matching Eligible Participant Description. Insurance Company General Principal Guaranteed Option [Member] Principal Guaranteed Option [Member] Principal Guaranteed Option. Common/Collective Trust PRIN LIFETIME HYBR 2045 CIT Z [Member] Principal Lifetime Hybrid 2045 Fund [Member] Principal Lifetime Hybrid 2045 Fund. Document Information [Table] Document Information [Table] EBP 001 EBP 001 [Member] EBP 001 plan. Common/Collective Trust PRIN LIFETIME HYB 2070 CIT Z [Member] Principal Lifetime Hybrid 2070 Fund [Member] Principal Lifetime Hybrid 2070 Fund. EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] Registered Investment Company Vgd Ttl Intl Stk Idx Inst Fund [Member] Vanguard Ttl International Stock Index Institutional Fund [Member] Vanguard Ttl International Stock Index Institutional Fund. Vanguard Group [Member] Vanguard Group [Member] Vanguard Group. Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Minimum age for employee eligible for catch-up contributions EBP Minimum Age of Employee eligible for Catch Up Contributions EBP Minimum Age of Employee Eligible for Catch Up Contributions. Entity Registrant Name Entity Registrant Name Subsequent Events EBP, Subsequent Event [Text Block] Investment income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Common Stock, Class A EBP, Employer, Common Stock, Class A [Member] Common/Collective Trust PRIN LIFETIME HYBR 2055 CIT Z [Member] Principal Lifetime Hybrid 2055 Fund [Member] Principal Lifetime Hybrid 2055 Fund. EBP, Tax Status [Table] EBP, Tax Status [Table] Liabilities EBP, Liability [Abstract] EBP, Participant-Directed [Member]