FAIR VALUES OF FINANCIAL INSTRUMENTS (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Assets:
Secured loans receivable, net	$ 215,775	$ 212,577
Marketable debt securities	43,000	43,300
Unsecured loans receivable, net	60,877	63,598
Liabilities:
Redeemable OP unitholder interests	113,908	102,837
Carrying amount
Assets:
Cash and cash equivalents	58,530	45,807
Secured loans receivable, net	215,775	212,577
Derivative instruments	0	11
Marketable debt securities	42,950	43,331
Unsecured loans receivable, net	60,887	63,598
Liabilities:
Senior notes payable and other debt, gross	7,264,105	6,180,443
Derivative instruments and other liabilities	90,751	80,815
Redeemable OP unitholder interests	113,908	102,837
Fair value
Assets:
Cash and cash equivalents	58,530	45,807
Secured loans receivable, net	221,225	216,315
Derivative instruments	0	11
Marketable debt securities	42,950	43,331
Unsecured loans receivable, net	64,001	65,219
Liabilities:
Senior notes payable and other debt, gross	7,327,567	6,637,691
Derivative instruments and other liabilities	90,751	80,815
Redeemable OP unitholder interests	$ 113,908	$ 102,837