Shareholders' Equity, Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance at December 31, 2020	$ 363,082	$ 364,316
Other comprehensive income (loss) before reclassifications	(8,492)	(20,943)
Amounts reclassified from accumulated other comprehensive income (loss)	(501)	(605)
Other comprehensive loss	(8,993)	(21,548)
Ending balance	366,678	305,383
Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance at December 31, 2020	21,759	9,369
Ending balance	12,766	(12,179)
Foreign Currency [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance at December 31, 2020	(245)	(494)
Other comprehensive income (loss) before reclassifications	88	(687)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Other comprehensive loss	88	(687)
Ending balance	(157)	(1,181)
Unrealized Holding Gains (Losses) on Available-for-sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance at December 31, 2020	22,004	9,863
Other comprehensive income (loss) before reclassifications	(8,580)	(20,256)
Amounts reclassified from accumulated other comprehensive income (loss)	(501)	(605)
Other comprehensive loss	(9,081)	(20,861)
Ending balance	$ 12,923	$ (10,998)