Accumulated Other Comprehensive Income (Changes in AOCI by Component) (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) [Roll Forward]
Beginning balance	[1]	$ (12,606)	$ 12,343	$ (18,999)	$ (6,295)
Other comprehensive income before reclassifications	[1]	6,033	8,508	12,339	27,278
Amounts reclassified from accumulated other comprehensive income	[1]	45	(40)	132	(172)
Net current-period other comprehensive income	[1]	6,078	8,468	12,471	27,106
Ending balance	[1]	(6,528)	20,811	(6,528)	20,811
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	[1]	(11,002)	18,918	(12,704)	386
Other comprehensive income before reclassifications	[1]	6,033	8,508	7,735	27,278
Amounts reclassified from accumulated other comprehensive income	[1]	0	(146)	0	(384)
Net current-period other comprehensive income	[1]	6,033	8,362	7,735	26,894
Ending balance	[1]	(4,969)	27,280	(4,969)	27,280
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	[1]	(1,604)	(6,575)	(6,295)	(6,681)
Other comprehensive income before reclassifications	[1]	0	0	4,604	0
Amounts reclassified from accumulated other comprehensive income	[1]	45	106	132	212
Net current-period other comprehensive income	[1]	45	106	4,736	212
Ending balance	[1]	$ (1,559)	$ (6,469)	$ (1,559)	$ (6,469)

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