Loans Receivable (Details) (USD $)	1 Months Ended	12 Months Ended
	Dec. 31, 2012 loan	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 NHP property	Dec. 21, 2012 Secured and unsecured loans	Dec. 31, 2012 Secured loans loan	Dec. 31, 2011 Secured loans loan	Dec. 31, 2012 Unsecured loans loan	Dec. 31, 2011 First mortgage loan maturing in 2016 [Member]
Accounts, Notes, Loans and Financing Receivable
Secured loans receivable, net	$ 697,100,000	$ 697,100,000	$ 276,200,000
Number of secured loans made	2
Loans receivable, aggregate principal amount	425,000,000
Loans receivable, weighted average interest rate	8.50%
Proceeds from loans receivable		43,219,000	220,179,000	19,291,000		37,600,000		218,500,000
Number of secured loans repaid							3	8	4
Mortgage loans receivable					271,700,000
Number of Properties Held as Security					53
Other unsecured loans					60,500,000
Principal amount of mortgage debt										12,900,000
Interest rate on loans issued (as a percent)										9.00%
Gain (loss) on repayment of loans receivable								$ 4,400,000