SENIOR NOTES PAYABLE AND OTHER DEBT (Details 4) (USD $)	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2012	$ 239,398,000
2013	941,773,000
2014	286,978,000
2015	1,097,854,000
2016	432,410,000
Thereafter	3,180,663,000
Total maturities	6,179,076,000	6,180,443,000
Unrestricted cash and cash equivalents	53,224,000	45,807,000	41,899,000	21,812,000
Unsecured revolving credit facilities
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	73,419,000	455,578,000
Unrestricted cash and cash equivalents	53,200,000
Amount outstanding, net of cash and cash equivalents	20,200,000
Mortgage loans
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	23,800,000	14,600,000
6.90% Senior Notes due 2037 | NHP
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Thereafter	52,400,000
6.59% senior notes due 2038 | NHP
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Thereafter	23,000,000
Principal Amount Due at Maturity
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2012	200,486,000
2013	895,571,000
2014	244,614,000
2015	989,941,000
2016	404,370,000
Thereafter	3,009,634,000
Total maturities	5,744,616,000
Unsecured Revolving Credit Facility
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2015	73,419,000
Total maturities	73,419,000
Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2012	38,912,000
2013	46,202,000
2014	42,364,000
2015	34,494,000
2016	28,040,000
Thereafter	171,029,000
Total maturities	$ 361,041,000