Debt Obligations (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 property	Mar. 31, 2012	Dec. 31, 2012 property
Debt Obligations
Amount outstanding under Unsecured Credit Agreement	$ 117,500,000		$ 115,500,000
Amount outstanding Senior Unsecured Notes	185,800,000		185,800,000
Bank Borrowings
Debt Obligations
Possible total maximum availability under Unsecured Credit Agreement			350,000,000
Maximum availability under Unsecured Credit Agreement			240,000,000
Decrease in drawn pricing, basis point (as a percent)	0.25%
Decrease in undrawn pricing, basis point (as a percent)	0.10%
Additional extension period option	1 year
Extension of maturity date	1 year
Description of interest rate	LIBOR
Basis spread over base rate (as a percent)	1.50%
Unused commitment fee (as a percent)	0.30%
Amount borrowed	2,000,000
Amount outstanding under Unsecured Credit Agreement	117,500,000
Amount available for borrowing under Unsecured Credit Agreement	122,500,000
Senior unsecured notes
Debt Obligations
Amount outstanding Senior Unsecured Notes	185,800,000		185,800,000
Weighted average interest rate (as a percent)	5.20%		5.20%
Uncommitted Private Shelf Agreement
Debt Obligations
Maximum available for issuance under private shelf agreement	100,000,000		100,000,000
Bonds payable
Debt Obligations
Weighted average interest rate (as a percent)	2.90%
Amount outstanding	2,035,000		2,635,000
Number of assisted living properties securing debt instruments	5		5
Repayments of debt	600,000	565,000
Aggregate carrying value of real estate property securing the entity's debt obligation	$ 6,584,000		$ 6,650,000