Dispositions of Real Estate and Discontinued Operations (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011 item	Dec. 31, 2010 item
Operating income from discontinued operations
Rental and related revenues	$ 13,025,000	$ 14,877,000	$ 19,293,000
Depreciation and amortization expenses	8,267,000	7,473,000	6,513,000
Operating expenses	22,000	22,000	263,000
Other expense, net	2,232,000	3,333,000	3,393,000
Income before gain on sales of real estate	2,504,000	4,049,000	9,124,000
Gain on sales of real estate	31,454,000	3,107,000	19,925,000
Number of properties held for sale		4	7
Number of properties sold	4	3	14
Number of properties included in discontinued operations	4	7	21
Senior housing
Dispositions of Real Estate and Land
Number of properties disposed	2	3
Total consideration for disposition of real estate	111,000,000	19,000,000
Medical office
Dispositions of Real Estate and Land
Total consideration for disposition of real estate	7,000,000
Post-acute/skilled nursing
Dispositions of Real Estate and Land
Total consideration for disposition of real estate	15,000,000
Parcel of land in the life science segment
Dispositions of Real Estate and Land
Total consideration for disposition of real estate	$ 18,000,000