Other Comprehensive Income (Loss) (Schedule of Other Comprehensive Income Components) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 668,459	$ 624,709	$ 573,820
Other Comprehensive Income (Loss) Before Reclassification	(278,532)	(18,116)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(390)	(1,775)
Total Other Comprehensive Income (Loss)	(278,922)	(19,891)	20,270
Ending balance	558,393	668,459	624,709
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	16,052	35,943
Other Comprehensive Income (Loss) Before Reclassification	(278,532)	(18,116)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(444)	(1,775)
Total Other Comprehensive Income (Loss)	(278,976)	(19,891)
Ending balance	(262,924)	16,052	35,943
Postretirement Benefit Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(568)	(568)
Other Comprehensive Income (Loss) Before Reclassification	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	54	0
Total Other Comprehensive Income (Loss)	54	0
Ending balance	(514)	(568)	(568)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	15,484	35,375	15,105
Total Other Comprehensive Income (Loss)	(278,922)	(19,891)	20,270
Ending balance	$ (263,438)	$ 15,484	$ 35,375