Schedule IV - Movement in Mortgage Loans on Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Beginning Balance	$ 20,294	$ 22,764	$ 24,238
Deductions during the year:
Early payoff of loan investment	0	(1,502)	0
Sale of loan investments	(8,256)	0	0
Principal payments received on loan investments	(897)	(904)	(1,339)
Amortization of discount and premiums	15	(64)	(135)
Valuation allowance	(992)	0	0
Ending Balance	$ 10,164	$ 20,294	$ 22,764