Pro Forma Information (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	5 Months Ended	9 Months Ended				12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended			1 Months Ended		1 Months Ended			1 Months Ended		1 Months Ended
	Oct. 31, 2011	Jul. 31, 2011	Sep. 30, 2011 property	Sep. 30, 2010	Sep. 30, 2011 property	Sep. 30, 2010 property	Dec. 31, 2010 property	Sep. 30, 2011 Acquisition	Sep. 30, 2011 Acquisition	Sep. 30, 2011 Sale property	Sep. 30, 2011 Senior living communities property	Sep. 30, 2011 Medical Office Building property	Dec. 31, 2010 Medical Office Building property	Sep. 30, 2011 Five Star	Sep. 30, 2011 Five Star	Dec. 31, 2010 Five Star	Dec. 31, 2010 Five Star Skilled nursing facilities	Dec. 31, 2010 Skilled nursing facilities property	Jan. 31, 2011 Senior unsecured notes 4.30%	Sep. 30, 2011 Senior unsecured notes 4.30%	Jun. 30, 2011 Unsecured revolving credit facility	Sep. 30, 2011 Unsecured revolving credit facility	Jun. 30, 2011 Previous unsecured revolving credit facility	Apr. 30, 2010 Senior unsecured notes 6.75%	Sep. 30, 2011 Senior unsecured notes 6.75%	May 31, 2010 Senior unsecured notes 7.875%
Pro Forma Information
Number of properties acquired											19	25	26
Aggregate purchase price of properties acquired, excluding closing costs								$ 43,725	$ 569,893				$ 433,955
Number of properties sold			2							7								4
Aggregate sale price										39,460								1,450
Gain on sale of properties				109	21,315	109									21,315		109
Real estate improvements purchased														10,554	25,877	31,894
Impairment of assets charges recorded			1,028		1,194	1,095	5,965
Number of properties impaired			1		3	5	7
Debt sold																			250,000					200,000
Interest rate (as a percent)																				4.30%					6.75%	7.875%
Deferred financing fees																			1,973					2,907
Unsecured revolving credit facility, maximum borrowing capacity																					750,000	750,000	550,000
Loss on early extinguishment of debt					(427)	(2,433)															(427)					2,433
Number of common shares issued	9,200,000	11,500,000			11,500,000		14,400,000
Redemption of senior notes																										97,500
Pro forma results of operations
Total revenues			121,642	119,601	362,174	359,367
Net income			$ 32,807	$ 30,899	$ 122,958	$ 125,235
Per common share data:
Net income (in dollars per share)			$ 0.21	$ 0.20	$ 0.80	$ 0.82