Reportable Segments (Revenues in Excess of Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information
Total property revenues in excess of expenses	$ 62,896	$ 44,849	$ 39,613
Domestic office investments
Segment Reporting Information
Total property revenues in excess of expenses	11,022	11,076	10,497
Domestic residential/living investments
Segment Reporting Information
Total property revenues in excess of expenses	6,151	4,008	2,977
Domestic retail investments
Segment Reporting Information
Total property revenues in excess of expenses	13,405	12,400	10,889
Domestic industrial investments
Segment Reporting Information
Total property revenues in excess of expenses	3,300	4,363	5,862
International industrial investments
Segment Reporting Information
Total property revenues in excess of expenses	16,261	1,645	0
International office investments
Segment Reporting Information
Total property revenues in excess of expenses	6,235	5,919	6,922
International residential/living investments
Segment Reporting Information
Total property revenues in excess of expenses	$ 6,522	$ 5,438	$ 2,466