Real Estate Properties (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended					12 Months Ended		12 Months Ended		1 Months Ended	12 Months Ended				1 Months Ended														12 Months Ended
	Dec. 31, 2012 sqft	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Above market lease	Dec. 31, 2011 Above market lease	Dec. 31, 2012 In-place lease intangibles	Dec. 31, 2011 In-place lease intangibles	Dec. 31, 2012 Below market lease	Dec. 31, 2011 Below market lease	May 31, 2011 Senior living communities Five Star Property	Dec. 31, 2012 Acquisition Senior living communities item	Dec. 31, 2011 Acquisition Senior living communities item	Dec. 31, 2012 Acquisition MOBs item	Dec. 31, 2011 Acquisition MOBs item	Jul. 31, 2012 Acquisition Florida MOBs item	Jul. 31, 2011 Acquisition Florida MOBs item	Jun. 30, 2011 Acquisition Florida MOBs item	Aug. 31, 2011 Acquisition Florida Land acre Property	Dec. 31, 2012 Acquisition Colorado MOBs item	Dec. 31, 2012 Acquisition Texas MOBs item	Jul. 31, 2012 Acquisition Texas MOBs item	May 31, 2012 Acquisition Georgia MOBs item	Dec. 31, 2012 Acquisition Minnesota MOBs item	May 31, 2011 Acquisition Minnesota MOBs item	Jan. 31, 2011 Acquisition Minnesota MOBs item	Nov. 30, 2011 Acquisition Virginia MOBs item	Dec. 31, 2011 Acquisition Indiana MOBs item	Jun. 30, 2012 Acquisition Hawaii MOBs item	Dec. 31, 2012 Sale	Dec. 31, 2011 Sale Property	Dec. 31, 2012 Sale MOBs Property	Dec. 31, 2011 Sale MOBs Property	Dec. 31, 2011 Sale Skilled nursing facilities Property	Dec. 31, 2011 Sale Assisted living community Property	Dec. 31, 2012 Properties acquired in 2012	Dec. 31, 2011 Properties acquired in 2011
Real estate properties
Number of properties sold or agreed to be sold																														7	1	2	4	1
Aggregate sale price																		$ 4,000											$ 1,100	$ 39,460
Number of properties acquired or agreed to be acquired										6	11	28	13	28	1	1	3	4	2	2	1	1	1	1	1	2	1	1
(Loss) gain on sale of properties	(101)	21,315	109																										(101)	21,315
Area of land (in acres)																		47
Intangible lease assets recorded	161,419	130,153		45,290	39,075	116,129	91,078						32,684	52,209	789	354	599		3,196	4,006	1,973	1,392	4,087	1,403	2,722	1,897	4,867	4,306							41,764	52,210
Intangible lease liabilities recorded	21,978	25,487											971	3,770			200		10	11		10	183	51				629							971	3,770
Accumulated amortization on lease assets				13,675	9,612	31,907	20,306	8,286	7,709
Weighted average amortization period				6 years 8 months 12 days		6 years 3 months 18 days		7 years 6 months
Expenditure committed relating to leases	6,599
Area of real estate properties leased (in square feet)	636,000
Committed but unspent tenant related obligations	6,033
Future amortization of intangible lease assets and liabilities
2013	24,419
2014	19,098
2015	14,532
2016	12,411
2017	10,255
Thereafter	$ 21,430