Debt Obligations (Details) (USD $)			12 Months Ended									1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Senior unsecured notes	Dec. 31, 2012 5.0% senior unsecured term notes due July 19 2024	Dec. 31, 2011 4.80% senior unsecured term notes due July 20, 2021	Dec. 31, 2011 Uncommitted Private Shelf Agreement	Dec. 31, 2010 5.25% senior unsecured term notes due July 14, 2015	Dec. 31, 2010 5.74% senior unsecured term notes due July 14, 2019	Dec. 31, 2012 Bonds payable property	Dec. 31, 2011 Bonds payable property	Dec. 31, 2012 Bank Borrowings	Jan. 31, 2013 Bank Borrowings Subsequent Event
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
Basis spread over base rate (as a percent)											1.25%	1.25%
Description of interest rate											LIBOR	LIBOR
Maximum ratio of total indebtedness to total asset value											0.5
Maximum ratio of secured debt to total asset value											0.35
Maximum ratio of unsecured debt to the value of the unencumbered asset pool											0.6
Minimum ratio of EBITDA to fixed charges											1.50
Unused commitment fee (as a percent)											0.25%	0.30%
Amount borrowed											153,500,000	2,000,000
Repayment amount											94,000,000
Amount outstanding under Unsecured Credit Agreement	115,500,000	56,000,000									115,500,000	117,500,000
Amount outstanding Senior Unsecured Notes	185,800,000	100,000,000	185,800,000
Amount available for borrowing under Unsecured Credit Agreement											124,500,000	122,500,000
Maximum available for issuance under private shelf agreement						100,000,000
Debt instrument, amount borrowed				85,800,000	50,000,000		25,000,000	25,000,000
Stated interest rate (as a percent)				5.00%	4.80%
Average life from the date of original issuance				12 years
Scheduled annual principal pay downs from year 8 through 12				17,160,000
Amount outstanding									2,635,000	3,200,000
Number of assisted living properties securing loan									5	5
Weighted average interest rate (as a percent)			5.20%						2.20%
Repayments of debt									565,000	530,000
Aggregate carrying value of real estate property securing the entity's debt obligation									6,650,000	6,915,000
Scheduled Principal Payments
Total	303,935,000		185,800,000						2,635,000		115,500,000
2013	600,000								600,000
2014	4,802,000		4,167,000						635,000
2015	30,566,000		29,166,000						1,400,000
2016	132,167,000		16,667,000								115,500,000
2017	14,167,000		14,167,000
Thereafter	$ 121,633,000		$ 121,633,000