Loans Receivable and Other Lending Investments, net (Credit Characteristics by Payment Status) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Recorded investment in loans, aged by payment status and presented by class
Current	$ 863,662	$ 1,062,944
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	60,725	231,877
Total Past Due	60,725	231,877
Loans	$ 924,387	$ 1,294,821
Financing receivable, number of loans greater than 90 days past due | loan	2	4
Financing receivables, past due time period	90 days	90 days
Minimum
Recorded investment in loans, aged by payment status and presented by class
Financing receivables, past due time period	4 years	1 year
Maximum
Recorded investment in loans, aged by payment status and presented by class
Financing receivables, past due time period	9 years	9 years
Senior mortgages
Recorded investment in loans, aged by payment status and presented by class
Current	$ 703,807	$ 719,057
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	60,725	75,343
Total Past Due	60,725	75,343
Loans	764,532	794,400
Corporate/Partnership loans
Recorded investment in loans, aged by payment status and presented by class
Current	149,663	334,364
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	0	156,534
Total Past Due	0	156,534
Loans	149,663	490,898
Subordinate mortgages
Recorded investment in loans, aged by payment status and presented by class
Current	10,192	9,523
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	0	0
Total Past Due	0	0
Loans	$ 10,192	$ 9,523