Other Comprehensive Income (Loss) (Schedule of Other Comprehensive Income Components) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ 458,640	$ 364,571	$ 330,267
Other Comprehensive Income (Loss) Before Reclassification	23,162	(3,943)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(959)	(535)
Comprehensive Income (Loss)	22,203	(4,478)	4,253
Ending Balance	573,820	458,640	364,571
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(6,759)	(2,335)
Other Comprehensive Income (Loss) Before Reclassification	23,418	(3,866)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(986)	(558)
Comprehensive Income (Loss)	22,432	(4,424)
Ending Balance	15,673	(6,759)	(2,335)
Postretirement Benefit Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(339)	(285)
Other Comprehensive Income (Loss) Before Reclassification	(256)	(77)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	27	23
Comprehensive Income (Loss)	(229)	(54)
Ending Balance	(568)	(339)	(285)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(7,098)	(2,620)	(6,404)
Comprehensive Income (Loss)	22,203	(4,478)	4,253
Ending Balance	$ 15,105	$ (7,098)	$ (2,620)