Accumulated Other Comprehensive Income (Changes in AOCI by Component) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (48,133)	$ (12,606)	$ (22,225)	$ (18,999)
Other comprehensive loss before reclassifications	[1]	(7,845)	6,033	(33,893)	12,339
Amounts reclassified from accumulated other comprehensive loss	[1]	57	45	40	132
Net current-period other comprehensive income (loss)	[1]	(7,788)	6,078	(33,853)	12,471
Ending balance		(55,921)	(6,528)	(55,921)	(6,528)
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(45,748)	(11,002)	(19,779)	(12,704)
Other comprehensive loss before reclassifications	[1]	(7,845)	6,033	(33,893)	7,735
Amounts reclassified from accumulated other comprehensive loss	[1]	(4)	0	(82)	0
Net current-period other comprehensive income (loss)	[1]	(7,849)	6,033	(33,975)	7,735
Ending balance		(53,597)	(4,969)	(53,597)	(4,969)
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(2,385)	(1,604)	(2,446)	(6,295)
Other comprehensive loss before reclassifications	[1]	0	0	0	4,604
Amounts reclassified from accumulated other comprehensive loss	[1]	61	45	122	132
Net current-period other comprehensive income (loss)	[1]	61	45	122	4,736
Ending balance		$ (2,324)	$ (1,559)	$ (2,324)	$ (1,559)
Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						$ 0
Accounting Standards Update 2016-01 [Member] | Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						157
Accounting Standards Update 2016-01 [Member] | Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						0
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						$ 157

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