NOTES PAYABLE TO BANKS (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 Percent	Dec. 31, 2010 Percent	Dec. 31, 2009	Dec. 31, 2011 Seven bank group unsecured revolving credit facility [Member] integer Percent	Dec. 31, 2011 PNC N.A. unsecured revolving credit facility [Member] Percent	Jan. 03, 2012 PNC N.A. unsecured revolving credit facility [Member] Percent
Line of Credit Facility [Line Items]
Unsecured revolving credit facility available borrowings				$ 200,000,000	$ 25,000,000
Banks included in the unsecured revolving credit facility group				7
Credit facility maturity date				January 2013	January 2013
Interest rate on the facility, LIBOR basis spread on variable rate (in hundredths)				0.85%	0.90%	1.65%
Annual facility fee				0.20
Weighted average interest rates (in hundredths)	1.41%	1.42%		1.148%	1.195%
Notes payable to banks	154,516,000	91,294,000		147,000,000	7,516,000
Additional remaining line of credit				53,000,000	17,484,000
Average bank borrowings	124,697,000	122,942,000
Weighted average interest rates (including amortization of loan costs) (in hundredths)	1.65%	1.68%
Amortization of bank loan costs	$ 300,000	$ 314,000	$ 297,000
Line of credit annual facility fee basis points minimum				15
Line of credit annual facility fee basis points maximum				20