SENIOR NOTES PAYABLE AND OTHER DEBT (Details 2) (USD $)					3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Unsecured revolving credit facilities	Dec. 31, 2012 Unsecured revolving credit facilities	Mar. 31, 2013 Mortgage loans	Dec. 31, 2012 Mortgage loans	Mar. 31, 2013 6.90% Senior Notes due 2037	Dec. 31, 2012 6.90% Senior Notes due 2037	Mar. 31, 2013 6.59% Senior Notes due 2038	Dec. 31, 2012 6.59% Senior Notes due 2038	Mar. 31, 2013 6.59% Senior Notes due 2038 NHP	Mar. 31, 2013 Principal Amount Due at Maturity	Mar. 31, 2013 Unsecured Revolving Credit Facility	Mar. 31, 2013 Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2013	$ 229,143,000													$ 190,394,000	$ 0	$ 38,749,000
2014	340,433,000													292,698,000	0	47,735,000
2015	1,271,345,000													1,068,219,000	164,734,000	38,392,000
2016	442,121,000													410,917,000	0	31,204,000
2017	941,709,000													922,714,000	0	18,995,000
Thereafter	5,004,838,000													4,851,972,000	0	152,866,000
Total	8,229,589,000	8,186,315,000			164,734,000	540,727,000	23,000,000	23,200,000	52,400,000	52,400,000	22,973,000	22,973,000	23,000,000	7,736,914,000	164,734,000	327,941,000
Interest rate (as a percent)									6.90%	6.90%	6.59%	6.59%
Unrestricted cash and cash equivalents	57,690,000	67,908,000	53,224,000	45,807,000	57,700,000
Amount outstanding, net of cash and cash equivalents					$ 107,000,000
Line of credit facility optional extension period					1 year