Other Real Estate Property Investments (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Acquisition
Consideration, Cash Paid	$ 172,380,000	$ 113,830,000
Consideration, Debt and Other Liabilities Assumed	35,120,000	57,869,000
Consideration, Noncontrolling Interest	27,432,000	1,500,000
Assets Acquired, Real Estate	184,564,000	159,231,000
Assets Acquired, Net Intangibles	50,368,000	13,968,000
Medical office
Acquisition
Consideration, Cash Paid	157,556,000	29,743,000
Consideration, Debt and Other Liabilities Assumed	35,120,000
Consideration, Noncontrolling Interest	27,346,000	1,500,000
Assets Acquired, Real Estate	170,443,000	26,191,000
Assets Acquired, Net Intangibles	49,579,000	5,052,000
Life science
Acquisition
Consideration, Cash Paid	7,964,000	84,087,000
Consideration, Debt and Other Liabilities Assumed		57,869,000
Consideration, Noncontrolling Interest	86,000
Assets Acquired, Real Estate	7,580,000	133,040,000
Assets Acquired, Net Intangibles	470,000	8,916,000
Number of facilities placed into service		2
The square footage of facilities placed in service		88,000
Senior housing
Acquisition
Consideration, Cash Paid	3,860,000
Assets Acquired, Real Estate	3,541,000
Assets Acquired, Net Intangibles	319,000
Hospital
Acquisition
Consideration, Cash Paid	3,000,000
Assets Acquired, Real Estate	3,000,000
Life science and medical office
Acquisition
Payments to acquire productive assets	$ 126,000,000	$ 87,000,000