Segment Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment
Segment Reporting [Abstract]
Number of reportable segments | segment	3	3	3
Intersegment activity	$ 0
Segment Reporting Information
Office building services costs	2,315,000	$ 2,319,000	$ 1,418,000
Operating Segments | Triple-net leased properties
Segment Reporting Information
Office building services costs	0	0	0
Operating Segments | Senior living operations
Segment Reporting Information
Office building services costs	0	0	0
Operating Segments | Office operations
Segment Reporting Information
Office building services costs	2,315,000	2,319,000	1,418,000
All Other
Segment Reporting Information
Office building services costs	$ 0	$ 0	$ 0