Schedule IV (Consolidated) - Mortgage Loans on Real Estate - Carrying Amount of Mortgage Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in carrying amount of mortgage loans
Balance at beginning of the year	$ 2,995	$ 242	$ 570
Additions during the year - new mortgage loans	1,471	2,821
Collections of principal	3,004	68	328
Balance at the end of the year	$ 1,462	$ 2,995	$ 242