Stockholders' Equity (Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Estimated tax benefit (provision)
Beginning balance	$ (22,000)	$ 9,000	$ 1,000
Other comprehensive income (loss) before reclassifications	188,000	(126,000)	174,000
Less: Amount reclassified from accumulated other comprehensive income (loss)	41,000	(95,000)	166,000
Net current period other comprehensive income (loss)	147,000	(31,000)	8,000
Ending balance	125,000	(22,000)	9,000
AOCI, after tax
Beginning balance	696,815,000	689,384,000	608,693,000
Other comprehensive income (loss) before reclassifications	(836,000)	542,000	(682,000)
Less: Amount reclassified from accumulated other comprehensive income (loss)	(152,000)	358,000	(626,000)
Net current period other comprehensive income (loss)	(684,000)	184,000	(56,000)
Ending balance	620,855,000	696,815,000	689,384,000
Unrealized gains (losses) on available-for-sale investments
AOCI, before tax
Beginning balance	(2,000)	(2,000)	(2,000)
Other comprehensive income (loss) before reclassifications	(320,000)	0	0
Less: Amount reclassified from accumulated other comprehensive income (loss)	0	0	0
Net current period other comprehensive income (loss)	(320,000)	0	0
Ending balance	(322,000)	(2,000)	(2,000)
Unrealized gains (losses) on derivatives
AOCI, before tax
Beginning balance	173,000	(42,000)	22,000
Other comprehensive income (loss) before reclassifications	(704,000)	668,000	(856,000)
Less: Amount reclassified from accumulated other comprehensive income (loss)	(193,000)	453,000	(792,000)
Net current period other comprehensive income (loss)	(511,000)	215,000	(64,000)
Ending balance	(338,000)	173,000	(42,000)
AOCI
AOCI, after tax
Beginning balance	149,000	(35,000)	21,000
Ending balance	$ (535,000)	$ 149,000	$ (35,000)