Stockholders' Equity (Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Estimated tax benefit (provision)
Beginning balance	$ 125,000	$ (22,000)	$ 9,000
Other comprehensive income (loss) before reclassifications	(540,000)	188,000	(126,000)
Less: Amount reclassified from accumulated other comprehensive income (loss)	(418,000)	41,000	(95,000)
Net current period other comprehensive income (loss)	122,000	147,000	31,000
Ending balance	3,000	125,000	(22,000)
AOCI, after tax
Beginning balance	620,855,000	696,815,000	689,384,000
Other comprehensive income (loss) before reclassifications	2,245,000	(836,000)	542,000
Less: Amount reclassified from accumulated other comprehensive income (loss)	1,574,000	(152,000)	358,000
Net current period other comprehensive income (loss)	671,000	(684,000)	184,000
Ending balance	535,495,000	620,855,000	696,815,000
Unrealized gains (losses) on available-for-sale investments
AOCI, before tax
Beginning balance	(322,000)	(2,000)	(2,000)
Other comprehensive income (loss) before reclassifications	448,000	(320,000)	0
Less: Amount reclassified from accumulated other comprehensive income (loss)	0	0	0
Net current period other comprehensive income (loss)	448,000	(320,000)	0
Ending balance	126,000	(322,000)	(2,000)
Unrealized gains (losses) on derivatives
AOCI, before tax
Beginning balance	(338,000)	173,000	(42,000)
Other comprehensive income (loss) before reclassifications	2,337,000	(704,000)	668,000
Less: Amount reclassified from accumulated other comprehensive income (loss)	1,992,000	(193,000)	453,000
Net current period other comprehensive income (loss)	345,000	(511,000)	215,000
Ending balance	7,000	(338,000)	173,000
AOCI
AOCI, after tax
Beginning balance	(535,000)	149,000	(35,000)
Ending balance	$ 136,000	$ (535,000)	$ 149,000