Significant Accounting Policies - Investment in Marketable Securities (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Investment in Marketable Securities
Commercial mortgage-backed securities	$ 9,797,000		$ 9,797,000		$ 11,240,000
Total investment in marketable securities	9,797,000		9,797,000		11,240,000
Proceeds from sale of marketable securities	0	$ 0	0	$ 0
Equity marketable securities	0		0		0
Marketable securities, unrealized loss		$ 6,200,000		$ 6,200,000
Commercial mortgage-backed securities
Investment in Marketable Securities
Commercial mortgage-backed securities	9,797,000		9,797,000		11,240,000
Cost basis of commercial mortgage-backed securities	11,500,000		11,500,000		11,500,000
Unrealized loss			1,700,000		300,000
Fair value of security in a continuous unrealized loss position for less than 12 months	$ 9,800,000		$ 9,800,000		$ 11,200,000