Changes in Accumulated Other Comprehensive Income Balances (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Jan. 01, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		$ (6,660)
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period		7,773	$ (395)
Tax effect on unrealized gains arising during the period		(1,632)	83
Other comprehensive income, net of tax		2,898	(279)
Reclassification of certain tax effects from accumulated other comprehensive income at January 1,2018	$ (2,600)
Ending Balance		(3,762)
Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(2,310)	(3,334)	(2,310)
Other comprehensive income (loss):
Change in net actuarial gain		35	27
Tax effect on change in net actuarial gain		(7)	(6)
Other comprehensive income, net of tax		28	21
Reclassification of certain tax effects from accumulated other comprehensive income at January 1,2018				$ (569)
Ending Balance		(3,306)	(2,858)	(2,310)
Unrealized Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	14,544	(3,326)	14,544
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period		7,773	(395)
Tax effect on unrealized gains arising during the period		(1,632)	83
Reclassification adjustment for realized (gain) losses included in investment gains and losses		(4,141)	15
Tax effect on reclassification adjustment for losses included in income tax expense		870	(3)
Other comprehensive income, net of tax		2,870	(300)
Reclassification of certain tax effects from accumulated other comprehensive income at January 1,2018				3,188
Ending Balance		(456)	439	14,544
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 12,234	(6,660)	12,234
Other comprehensive income (loss):
Change in net actuarial gain		35	27
Tax effect on change in net actuarial gain		(7)	(6)
Unrealized holding gains (losses) arising during the period		7,773	(395)
Tax effect on unrealized gains arising during the period		(1,632)	83
Reclassification adjustment for realized (gain) losses included in investment gains and losses		(4,141)	15
Tax effect on reclassification adjustment for losses included in income tax expense		870	(3)
Other comprehensive income, net of tax		2,898	(279)
Reclassification of certain tax effects from accumulated other comprehensive income at January 1,2018				2,619
Ending Balance		$ (3,762)	$ (2,419)	12,234
Accounting Standards Update 2016-01 [Member] | Unrealized Gain (Loss) [Member]
Other comprehensive income (loss):
Cumulative effect of adoption of updated accounting guidance for equity financial instruments at January 1,2018				(16,993)
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Other comprehensive income (loss):
Cumulative effect of adoption of updated accounting guidance for equity financial instruments at January 1,2018				$ (16,993)