Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss), beginning balance	$ (19,757)
Net other comprehensive income (loss)	472	$ (10,058)	$ (890)
Reclassification of income tax effects due to the adoption of ASU 2018-02	0
Accumulated other comprehensive income (loss), ending balance	(23,510)	(19,757)
Net Unrealized Gains on AFS Securities [Member]
Accumulated other comprehensive income (loss), beginning balance	(6,825)	1,051	4,222
Other comprehensive income (loss) before reclassifications, net of tax	621	(7,876)	(3,171)
Amounts reclassified from accumulated other comprehensive income, net of tax	0	0	0
Net other comprehensive income (loss)	621	(7,876)	(3,171)
Reclassification of income tax effects due to the adoption of ASU 2018-02	(1,330)
Accumulated other comprehensive income (loss), ending balance	(7,534)	(6,825)	1,051
Net Unrealized Losses on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss), beginning balance	(300)	(43)	(287)
Other comprehensive income (loss) before reclassifications, net of tax	(551)	(257)	(53)
Amounts reclassified from accumulated other comprehensive income, net of tax	499	0	297
Net other comprehensive income (loss)	(52)	(257)	244
Reclassification of income tax effects due to the adoption of ASU 2018-02	(76)
Accumulated other comprehensive income (loss), ending balance	(428)	(300)	(43)
Pension Benefit Adjustment [Member]
Accumulated other comprehensive income (loss), beginning balance	(12,632)	(10,707)	(12,744)
Other comprehensive income (loss) before reclassifications, net of tax	(741)	(2,588)	1,102
Amounts reclassified from accumulated other comprehensive income, net of tax	644	663	935
Net other comprehensive income (loss)	(97)	(1,925)	2,037
Reclassification of income tax effects due to the adoption of ASU 2018-02	(2,819)
Accumulated other comprehensive income (loss), ending balance	(15,548)	(12,632)	(10,707)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss), beginning balance	(19,757)	(9,699)	(8,809)
Other comprehensive income (loss) before reclassifications, net of tax	(671)	(10,721)	(2,122)
Amounts reclassified from accumulated other comprehensive income, net of tax	1,143	663	1,232
Net other comprehensive income (loss)	472	(10,058)	(890)
Reclassification of income tax effects due to the adoption of ASU 2018-02	(4,225)
Accumulated other comprehensive income (loss), ending balance	$ (23,510)	$ (19,757)	$ (9,699)