Accumulated Other Comprehensive Income Balances Of Each Component Of Accumulated Other Comprehensive Income, Net Of Tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 949
Other comprehensive income (loss)	1,143	$ (1,309)
Ending balance	2,092
Unrealized Gains and Losses On Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	981	16,003
Cumulative effect adjustment for adoption of new accounting standards	0	(13,616)
Other comprehensive income before reclassifications	1,143	(1,309)
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss)	1,143	(1,309)
Ending balance	2,124	1,078
Postretirement Benefits Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(32)	(58)
Cumulative effect adjustment for adoption of new accounting standards	0	(11)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss)	0	0
Ending balance	(32)	(69)
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	949	15,945
Cumulative effect adjustment for adoption of new accounting standards	0	(13,627)
Other comprehensive income before reclassifications	1,143	(1,309)
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss)	1,143	(1,309)
Ending balance	$ 2,092	$ 1,009