Schedule IV - Mortgage Loans on Real Estate (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Mortgage Loans On Real Estate [Line Items]
Face Amount of Mortgages	$ 1,250,000
Carrying Amount of Mortgages	1,250,000	$ 8,661,000	$ 10,930,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	750,000
Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of year	8,661,000	10,930,000	14,430,000
New mortgage loans	0	500,000	7,307,000
Collections of principal	(4,142,000)	(2,319,000)	(10,807,000)
Foreclosures	(3,269,000)	(450,000)	0
Balance at the close of year	$ 1,250,000	8,661,000	10,930,000
Payments to acquire mortgage notes receivable		$ 500,000	$ 7,307,000
Marlow Heights, MD
Mortgage Loans On Real Estate [Line Items]
Interest Rate	7.00%
Maturity Date	May 14, 2016
Prior Liens	$ 0
Face Amount of Mortgages	750,000
Carrying Amount of Mortgages	750,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 750,000
4 properties in FL and GA
Mortgage Loans On Real Estate [Line Items]
Number of Properties | property	4
Corpus Christi, TX
Mortgage Loans On Real Estate [Line Items]
Interest Rate	4.50%
Maturity Date	Mar. 01, 2018
Prior Liens	$ 0
Face Amount of Mortgages	500,000
Carrying Amount of Mortgages	500,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0