Changes in Accumulated Other Comprehensive Income Balances (Schedule of Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 12,234			$ 12,234
Other comprehensive income:
Change in net actuarial gain		$ 26	$ 35	53	$ 70
Tax effect on change in net actuarial gain		(5)	(12)	(11)	(24)
Net unrealized holding gains (losses) arising during the period		1,962	2,654	1,567	7,900
Tax effect on unrealized gains arising during the period		(412)	(929)	(329)	(2,765)
Reclassification adjustment for realized gains included in investment gains and losses		(22)	10	(7)	(2,491)
Tax effect on reclassification adjustment for realized gains included in income tax expense		5	(3)	2	872
Other comprehensive income (loss), net of tax		1,554	1,755	1,275	3,562
Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018	(2,600)
Ending Balance		(865)		(865)
Minimum Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(2,310)			(2,310)	(2,666)
Other comprehensive income:
Change in net actuarial gain				53	70
Tax effect on change in net actuarial gain				(11)	(24)
Other comprehensive income (loss), net of tax				42	46
Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018				(569)
Ending Balance		(2,837)	(2,620)	(2,837)	(2,620)
Unrealized Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	14,544			14,544	13,037
Other comprehensive income:
Net unrealized holding gains (losses) arising during the period				1,567	7,900
Tax effect on unrealized gains arising during the period				(329)	(2,765)
Reclassification adjustment for realized gains included in investment gains and losses				(7)	(2,491)
Tax effect on reclassification adjustment for realized gains included in income tax expense				2	872
Other comprehensive income (loss), net of tax				1,233	3,516
Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018				3,188
Cumulative Effect of New Accounting Principle in Period of Adoption		(16,993)		(16,993)
Ending Balance		1,972	16,553	1,972	16,553
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 12,234			12,234	10,371
Other comprehensive income:
Change in net actuarial gain				53	70
Tax effect on change in net actuarial gain				(11)	(24)
Net unrealized holding gains (losses) arising during the period				1,567	7,900
Tax effect on unrealized gains arising during the period				(329)	(2,765)
Reclassification adjustment for realized gains included in investment gains and losses				(7)	(2,491)
Tax effect on reclassification adjustment for realized gains included in income tax expense				2	872
Other comprehensive income (loss), net of tax				1,275	3,562
Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018				2,619
Cumulative Effect of New Accounting Principle in Period of Adoption		(16,993)		(16,993)
Ending Balance		$ (865)	$ 13,933	$ (865)	$ 13,933