INVESTMENTS IN UNCONSOLIDATED ENTITIES (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2012	Sep. 30, 2012 property	Sep. 30, 2011	Sep. 30, 2012 property	Sep. 30, 2011	Dec. 31, 2011 property
INVESTMENTS IN UNCONSOLIDATED ENTITIES
Management fees earned in connection with unconsolidated entities		$ 2,000,000	$ 1,900,000	$ 5,700,000	$ 3,700,000
Equity method investments
Number of real estate properties		1,450		1,450
Investment in joint ventures	12,500,000
Number of properties accounted for under equity method		55		55		92
Net investments in unconsolidated entities		90,992,000		90,992,000		105,303,000
Income (loss) from unconsolidated entities	16,600,000	17,074,000	182,000	17,905,000	(71,000)
Thirty six medical office buildings
Equity method investments
Number of real estate properties	36
Number of real estate properties marketed for sale	1
Purchase of joint venture interests	350,000,000
Notes payable and other debt	101,600,000
Total purchase consideration	380,000,000
Fair value of previously held equity interest	30,000,000
Gain on re-measurement of equity method investments	$ 16,600,000
Medical office buildings
Equity method investments
Number of real estate properties		322		322
Minimum
Equity method investments
Ownership interests in properties accounted for under the equity method (as a percent)		5.00%		5.00%		5.00%
Minimum | Thirty six medical office buildings
Equity method investments
Ownership interests in properties accounted for under the equity method (as a percent)	80.00%
Maximum
Equity method investments
Ownership interests in properties accounted for under the equity method (as a percent)		25.00%		25.00%		25.00%
Maximum | Thirty six medical office buildings
Equity method investments
Ownership interests in properties accounted for under the equity method (as a percent)	95.00%