Note 4 - Mortgage and Other Indebtedness (Details) (USD $)	1 Months Ended			3 Months Ended
	Mar. 31, 2014	Feb. 28, 2014	Jan. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	0.15%			0.15%
Line of Credit Facility, Maximum Borrowing Capacity	$ 145,000,000			$ 145,000,000
Line of Credit Facility, Remaining Borrowing Capacity	49,800,000			49,800,000
Number of Real Estate Properties	68			68
Line of Credit Facility, Additional Borrowing Capacity	120,000,000			120,000,000
Long-term Debt	871,334,000			871,334,000		857,144,000
Letters of Credit Outstanding, Amount	5,200,000			5,200,000
Proceeds from Loans				41,329,000	48,784,000
Repayments of Long-term Debt				27,137,000	1,728,000
Proceeds from Unsecured Lines of Credit		14,700,000
Repayments of Unsecured Debt	14,700,000
Repayments of Debt			4,000,000
Proceeds from Construction Loans Payable				19,800,000
Long-term Debt, Percentage Bearing Fixed Interest, Amount	271,200,000			271,200,000
Long-term Debt, Percentage Bearing Variable Interest, Amount	600,000,000			600,000,000
In Addition [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Number of Real Estate Properties	4			4
Unencumbered [Member] | Wholly Owned Properties [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Number of Real Estate Properties	54			54
Long-term Debt	230,000,000			230,000,000
Unencumbered [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Number of Real Estate Properties	63			63
Line of Credit [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Long-term Debt	145,000,000			145,000,000		145,000,000
Line of Credit [Member] | Minimum [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.42%			5.42%
Line of Credit [Member] | Maximum [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	6.78%			6.78%
Beacon Hill [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Debt Instrument, Face Amount	6,900,000			6,900,000
Scheduled Principal Payments [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Repayments of Long-term Debt				1,500,000
Fixed Rate Debt [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Long-term Debt	271,242,000			271,242,000
Long-term Debt, Fair Value	287,100,000			287,100,000
Variable Rate Debt [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Long-term Debt, Fair Value	598,800,000			598,800,000
Revolving Credit Facility [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	200,000,000			200,000,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 49,800,000			$ 49,800,000
Minimum [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate				1.80%
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	1.80%			1.80%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	2.78%			2.78%
Maximum [Member]
Note 4 - Mortgage and Other Indebtedness (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate				2.94%
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	3.58%			3.58%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.33%			5.33%