Debt Obligations (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012 property	Mar. 31, 2011	Dec. 31, 2011 property
Debt Obligations
Amount outstanding under Unsecured Credit Agreement	$ 73,000,000		$ 56,000,000
Bank Borrowings
Debt Obligations
Possible total maximum availability under Unsecured Credit Agreement	250,000,000
Maximum availability under Unsecured Credit Agreement	210,000,000
Amount borrowed under Unsecured Credit Agreement	17,000,000
Amount outstanding under Unsecured Credit Agreement	73,000,000
Amount available for borrowing under Unsecured Credit Agreement	137,000,000
Bank Borrowings | LIBOR
Debt Obligations
Basis spread over base rate (as a percent)	1.50%
Description of interest rate	LIBOR
Senior unsecured notes
Debt Obligations
Amount outstanding under Senior Unsecured Notes	100,000,000		100,000,000
Uncommitted Private Shelf Agreement
Debt Obligations
Maximum available for issuance under private shelf agreement	100,000,000		100,000,000
Issuance period (in years)			3
Bonds payable
Debt Obligations
Amount outstanding	2,635,000		3,200,000
Number of assisted living properties securing loan	5		5
Weighted average interest rate (as a percent)	2.20%
Repayments of debt	565,000	530,000
Aggregate carrying value of real estate property securing the entity's debt obligation	$ 6,849,000		$ 6,915,000