Significant Accounting Policies - Investment in Marketable Securities (Narrative) (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2024 USD ($) security	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Real Estate [Line Items]
Proceeds from sale of marketable securities	$ 0	$ 0
Equity marketable securities	0		$ 0
Commercial mortgage-backed securities
Real Estate [Line Items]
Cost basis of commercial mortgage backed securities	$ 11,500,000		11,500,000
Number of securities in unrealized gain position | security	1
Unrealized gain	$ 100,000
Fair market value	5,400,000
Unrealized loss	900,000		1,900,000
Fair value of security in a continuous unrealized loss position for less than 12 months	$ 5,300,000		$ 9,600,000
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, number of positions | security	1