SENIOR NOTES PAYABLE AND OTHER DEBT (Details 4) (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2012	$ 128,199,000
2013	948,913,000
2014	327,018,000
2015	1,430,396,000
2016	445,845,000
Thereafter	3,680,348,000
Total maturities	6,960,719,000	6,180,443,000
Unrestricted cash and cash equivalents	52,803,000	45,807,000	26,702,000	41,899,000	21,812,000
Unsecured revolving credit facilities
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	366,991,000	455,578,000
Unrestricted cash and cash equivalents	52,800,000
Amount outstanding, net of cash and cash equivalents	314,200,000
Mortgage loans
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
Total maturities	23,600,000	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	99,549,000
2013	898,439,000
2014	280,701,000
2015	1,025,773,000
2016	415,334,000
Thereafter	3,502,118,000
Total maturities	6,221,914,000
Unsecured Revolving Credit Facility
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2015	366,991,000
Total maturities	366,991,000
Scheduled Periodic Amortization
Scheduled maturities of borrowing arrangements and other provisions excluding capital lease obligations
2012	28,650,000
2013	50,474,000
2014	46,317,000
2015	37,632,000
2016	30,511,000
Thereafter	178,230,000
Total maturities	$ 371,814,000