Accumulated Other Comprehensive Income (Changes in AOCI by Component) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (55,921)	$ (6,528)	$ (22,225)	$ (18,999)
Other comprehensive loss before reclassifications	[1]	(14,149)	549	(48,043)	12,888
Amounts reclassified from accumulated other comprehensive loss	[1]	61	46	102	178
Net current-period other comprehensive income (loss)	[1]	(14,088)	595	(47,941)	13,066
Ending balance		(70,009)	(5,933)	(70,009)	(5,933)
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(53,597)	(4,969)	(19,779)	(12,704)
Other comprehensive loss before reclassifications	[1]	(14,149)	549	(48,043)	8,284
Amounts reclassified from accumulated other comprehensive loss	[1]	0	0	(81)	0
Net current-period other comprehensive income (loss)	[1]	(14,149)	549	(48,124)	8,284
Ending balance		(67,746)	(4,420)	(67,746)	(4,420)
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(2,324)	(1,559)	(2,446)	(6,295)
Other comprehensive loss before reclassifications	[1]	0	0	0	4,604
Amounts reclassified from accumulated other comprehensive loss	[1]	61	46	183	178
Net current-period other comprehensive income (loss)	[1]	61	46	183	4,782
Ending balance		$ (2,263)	$ (1,513)	$ (2,263)	$ (1,513)
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.