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Note 5 - Related-party Transactions (Details Textual)			1 Months Ended		3 Months Ended	12 Months Ended
Note 5 - Related-party Transactions (Details Textual)	Jan. 18, 2020 USD ($)	Jul. 31, 2018 USD ($)	Nov. 30, 2020 BRL (R$)	May 31, 2020 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	May 26, 2021	Mar. 25, 2021 USD ($)	Jul. 08, 2020 USD ($)	Dec. 31, 2018 USD ($)
SPAR BSMT Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					51.00%
William Bartels [Member] \| Loans Payable [Member]
Debt Instrument, Face Amount								$ 100,000
Debt Instrument, Interest Rate, Stated Percentage								2.00%
William Bartels [Member] \| Loans Payable [Member] \| Forecast [Member]
Debt Instrument, Interest Rate, Stated Percentage							6.00%
Security Advances [Member]
Reserve for Related-party Receivables										$ 901,000
NMS [Member] \| Minimum [Member]
Percent of Reimbursement					4.00%
NMS [Member] \| Maximum [Member]
Percent of Reimbursement					10.00%
JKC [Member] \| SPAR BSMT Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					39.00%
EILLC [Member] \| SPAR BSMT Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					10.00%
NMS [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
NSRS [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					100.00%
Resource Plus, Inc [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
RJ Holdings [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					50.00%
Meridian [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Meridian [Member] \| FRIEDSHELF 401 Proprietary Limited [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					23.00%
Meridian [Member] \| Lindicom Proprietary Limited [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					26.00%
SPAR Todopromo [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
Robert G. Brown and William H. Bartels [Member] \| SPAR Group [Member]
Percentage of Stockholders' Shares					53.20%
SAS [Member] \| Return of Security Advances and Preimum Advances [Member]
Due from Related Parties, Total									$ 901,000
SAS [Member] \| Security Advances [Member]
Due from Related Parties, Total									675,000
SAS [Member] \| Premium Advances [Member]
Due from Related Parties, Total									226,000
SAS [Member] \| Premium Adjustments [Member]
Related Party Transaction, Amounts of Transaction						$ 220,558
SAS [Member] \| Remaining Premium Adjustments [Member]
Related Party Transaction, Amounts of Transaction						1,102,790
SAS [Member] \| SMF [Member]
Security Deposit		$ 675,000
Due from Related Parties, Total		226,000							$ 226,000
Affinity Insurance Company, Ltd. [Member]
Related Party Deposit Liabilities		965,000
Affinity Insurance Company, Ltd. [Member] \| SMF [Member]
Proceeds from Security Deposit Refund		$ 426,795
Affinity Insurance Company, Ltd. [Member] \| SMF [Member] \| Monies Advanced By SMF to SAS for Quarterly Premium Installments [Member]
Related Party Transaction, Amount Refunded				$ 94,414
NMS [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Operating Lease, Expense Per Month					$ 2,000
Resource Plus, Inc [Member]
Majority Interest Ownership Percentage By Parent					51.00%
SPAR Todopromo [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Mr. Juan F. Medina Domenzain [Member] \| CON [Member]
Related Party Ownership Percentage					90.00%
Peter Brown [Member] \| Initiation Fee for Acquisition Strategy Services [Member] \| SPAR BSMT Joint Venture [Member]
Related Party Transaction, Amounts of Transaction \| R$			R$ 30,000
Peter Brown [Member] \| Monthly Fee for Acquisition Strategy Services [Member] \| SPAR BSMT Joint Venture [Member]
Related Party Transaction, Amounts of Transaction \| R$			R$ 15,000
William Bartels [Member]
Five Yer Period Agreement, Retirement Compensation	$ 100,000
Five Year Period Agreement, Annual Regular Fees	55,000
Five Year Period Agreement, Annual Supplemental Fees	50,000
Five Year Period Agreement, Annual Medical Benefits	$ 15,588
William Bartels [Member] \| SPAR Group [Member]
Percentage of Stockholders' Shares					25.10%
Pension and Other Postretirement Benefits Cost (Reversal of Cost), Total						$ 700,000