Accumulated Other Comprehensive Income (Changes in AOCI by Component) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (6,528)	$ 20,811	$ (18,999)	$ (6,295)
Other comprehensive income before reclassifications	[1]	549	(4,049)	12,888	23,229
Amounts reclassified from accumulated other comprehensive income	[1]	46	(257)	178	(429)
Net current-period other comprehensive income	[1]	595	(4,306)	13,066	22,800
Ending balance		(5,933)	16,505	(5,933)	16,505
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(4,969)	27,280	(12,704)	386
Other comprehensive income before reclassifications	[1]	549	(4,049)	8,284	23,229
Amounts reclassified from accumulated other comprehensive income	[1]	0	(364)	0	(748)
Net current-period other comprehensive income	[1]	549	(4,413)	8,284	22,481
Ending balance		(4,420)	22,867	(4,420)	22,867
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(1,559)	(6,469)	(6,295)	(6,681)
Other comprehensive income before reclassifications	[1]	0	0	4,604	0
Amounts reclassified from accumulated other comprehensive income	[1]	46	107	178	319
Net current-period other comprehensive income	[1]	46	107	4,782	319
Ending balance		$ (1,513)	$ (6,362)	$ (1,513)	$ (6,362)

[1] All amounts are net of tax. Amounts in parenthesis indicate debits.