Accumulated Other Comprehensive Income Balances Of Each Component Of Accumulated Other Comprehensive Income, Net Of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			$ 15,945
Cumulative effect adjustment for adoption of new accounting standards					$ 0
Other comprehensive income before reclassifications	$ (203)	$ 920	(1,512)	$ 2,017
Amounts reclassified from accumulated other comprehensive income	0	(53)	0	(110)
Other comprehensive (loss) income	(203)	867	(1,512)	1,907
Ending balance	806		806
Unrealized Gains and Losses On Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	1,078	12,910	16,003	11,871
Cumulative effect adjustment for adoption of new accounting standards					(13,616)
Other comprehensive income before reclassifications	(203)	920	(1,512)	2,017
Amounts reclassified from accumulated other comprehensive income	0	(55)	0	(113)
Other comprehensive (loss) income	(203)	865	(1,512)	1,904
Ending balance	875	13,775	875	13,775
Postretirement Benefits Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(69)	(109)	(58)	(110)
Cumulative effect adjustment for adoption of new accounting standards					(11)
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	0	2	0	3
Other comprehensive (loss) income	0	2	0	3
Ending balance	(69)	(107)	(69)	(107)
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	1,009	12,801	15,945	11,761
Cumulative effect adjustment for adoption of new accounting standards					$ (13,627)
Ending balance	$ 806	$ 13,668	$ 806	$ 13,668