Note B - Summary of Significant Accounting Policies (Details Textual)	3 Months Ended	6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2022	Jun. 30, 2021 USD ($)
Number of Parking Tenants or Operators	13	14	13
Immaterial Error Correction to the Consolidated Statements of Operations For Property Taxes [Member]
Increase (Decrease) in Property and Other Taxes Payable	$ 255,000		$ 510,000
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Parking Facilities, Operator, SP+Corporation [Member]
Concentration Risk, Percentage		59.40%	63.30%
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Parking Facilities, Operator, Premier Parking Service, LLC [Member]
Concentration Risk, Percentage		13.30%	13.30%
Real Estate Owned [Member] | Geographic Concentration Risk [Member] | Cincinnati [Member]
Concentration Risk, Percentage		19.10%	8.10%
Real Estate Owned [Member] | Geographic Concentration Risk [Member] | Detroit [Member]
Concentration Risk, Percentage		12.70%	19.00%
Real Estate Owned [Member] | Geographic Concentration Risk [Member] | Chicago [Member]
Concentration Risk, Percentage		8.80%	0.00%
Real Estate Owned [Member] | Geographic Concentration Risk [Member] | Houston [Member]
Concentration Risk, Percentage		7.80%	11.70%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Parking Facilities, Operator, SP+Corporation [Member]
Concentration Risk, Percentage		61.70%	25.40%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Parking Facilities, Operator, Premier Parking Service, LLC [Member]
Concentration Risk, Percentage			23.60%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Parking Facilities, Operator, ABM Parking Services Inc [Member]
Concentration Risk, Percentage			13.00%