Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance			$ 330,267
Other Comprehensive Income (Loss) Before Reclassification	$ 6,566	$ 3,983	10,564	$ 8,012
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0	(629)	0	(629)
Total Other Comprehensive Income	6,566	3,354	10,564	7,383
Ending Balance	354,954		354,954
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(2,314)	7,919	(6,312)	3,890
Other Comprehensive Income (Loss) Before Reclassification	6,566	3,983	10,564	8,012
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0	(629)	0	(629)
Total Other Comprehensive Income	6,566	3,354	10,564	7,383
Ending Balance	4,252	11,273	4,252	11,273
Postretirement Benefit Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(92)	(78)	(92)	(78)
Other Comprehensive Income (Loss) Before Reclassification	0	0	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0	0	0	0
Total Other Comprehensive Income	0	0	0	0
Ending Balance	(92)	(78)	(92)	(78)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(2,406)	7,841	(6,404)	3,812
Ending Balance	$ 4,160	$ 11,195	$ 4,160	$ 11,195