Schedule IV - Mortgage Loans on Real Estate (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Mortgage Loans on Real Estate [Abstract]
Face Amount of Mortgages	$ 0
Carrying amount of mortgages	0	$ 1,250,000	$ 8,661,000
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of year	1,250,000	8,661,000	10,930,000
New mortgage loans	0	0	500,000
Collections of principal	(1,250,000)	(4,142,000)	(2,319,000)
Foreclosures	0	(3,269,000)	(450,000)
Balance at the close of year	$ 0	$ 1,250,000	8,661,000
Payments to acquire mortgage notes receivable			$ 500,000